|“||To crush Itoshi Sae is what my football is all about||”|
— Rin, 
Rin Itoshi (糸師 凛, Itoshi Rin) is the deuteragonist of the Blue Lock (Manga).
Rin is the younger brother of Sae Itoshi and started playing football with him at a young age. Rin played as a forward on every team he was on, always being one of the top players. In Blue Lock, Rin is regarded as the best player until he is officially confirmed to be the #1 player by Jinpachi Ego. 
Rin's main goal is to become the world's best striker and in turn get revenge on his brother for discarding their dream of becoming the best in the world. Out of the original 300 forwards chosen to be apart of the Blue Lock Project, Rin is an ideal candidate for the type of striker Ego strives to create and thus Rin is the captain and center forward of the Blue Lock Eleven team against the Japan U-20.
Rin is a surprisingly tall teenager with a slim but powerful build. He is noticeably taller than Yoichi Isagi who is older than him. He has black hair with a bang going across his face more in his right eye than left eye, slim teal eyes, and distinct eyelashes that he shares with his brother Itoshi Sae. As a young boy, Rin looks largely the same, his facial features just become more distinct as he gets older.
At Blue Lock, Rin wears the standard issued body suit (black with gray stripes) and tracksuit. During Second Selection, he wore Team Red's #1 jersey and wore Team A's #1 black jersey during the Third Selection. Only once the Japan National Representative match begins does he don an official blue Blue Lock player uniform with the jersey #10 and a captain's armband.
At a young boy, Rin was very innocent and in awe of his brother, Sae, wanting nothing more than to become a cool and strong player like him. He started playing football because his brother told him to, following his orders without question. As they played football together, Rin listened to whatever Sae said and adjusted accordingly. When Sae left for Spain, Rin found football was more difficult without his brother but strived to become just like him and replace him. This is where Rin's core style of play would begin to shift from his instinctive style, to a more logical style.
Initially, he was a good team player and captain for his high-school team, appearing to be on good terms with some of his teammates. However, due to his fallout with his brother, he is often cold, blunt, and serious. He is entirely focused on soccer, to an almost obsessive degree and is also very egoistic, as he is always putting his goals first over everybody and their motivations. Rin has a lot of pride as a striker, which borders on arrogance, since he frequently describes other people's soccer and way of thinking as "lukewarm". These mannerisms and behaviors came from his brother; In an attempt to be like his brother, Rin copies his words and embodies his mindset.
Rin seems to respect almost nobody. He will only acknowledge your presence if you have a noticeable and annoying ability/influence on the soccer field. He seems to have no friends, only rivals (with only Isagi and Bachira seemingly being on generally even terms with him). By the time of the Japan National Representative match he is more noticeably talkative with the team, giving instruction on the pitch and conversing with Isagi specifically.
Rin commits to a routine of aftercare at the end of each and every day, to improve his physique, and he is often found in the training room doing drills or weights. Despite his arrogance and aloofness, Rin truly lives and breathes soccer, dedicating every waking moment to improving himself. This mentality combined with his personality is what makes him the top candidate for Blue Lock's supposed best striker. Everything Rin does is to enable him to beat his older brother and end the rivalry but after Rin moves past his revenge against his brother and his rivalry with teammates, he reaches a clarity in his decisions. He now aims to free himself from anything that ties him down and establish his own identity as an egoist, without relying on his brother, teammates or rivals.
- Playmaker: A player who controls the flow of the team's offensive play, and is often involved in passing moves which lead to goals, through their vision, technique, ball control, creativity, and passing ability.
When he was younger, Rin was an instinctual player but being trained and guided by his brother made him develop a notably logical and predictive style of playing. Whether on offense or defense, Rin's playstyle consists of him grasping the abilities of both his teammates and his opponents and forcing out their best plays and abilities, manipulating them in his efforts to score goals for himself.
Superior Football Technique: Rin is one of two players in Blue Lock who has top tier stats, along with Ryusei Shidou. During the Third Selection, he scored an average 2.5 goals a game, which was the highest among the Top 6. His spatial awareness, ball control, power, and kick accuracy are only rivaled by a handful of players. Though Shidou can be described similarly, the thing that makes Rin the best in Blue Lock is his willingness to cooperate with and create chemical reactions with his teammates, while Shidou scores goals completely independently. Rin's experience and techniques are advanced enough that he is able to play the role of captain, act as the focal point for an offense, play in defense and even overcome high-level defenders, using their own strengths against them.
Perfect Kick Accuracy: Rin's primary weapon is his highly accurate kick. His shooting/passing accuracy is near perfect, as demonstrated when he kicked two balls in such a way that they travelled different trajectories, yet still hit each other in mid-air. Rin's kicks are so accurate that he is able to score from long distance; Isagi implied that he could potentially score from anywhere below 35 meters, free kicks and even directly from corner kicks. Even when being physically pressured by players like Shidou Ryusei or Tabito Karasu, he is able to make a pinpoint shot. Oliver Aiku notes that his shot power and accuracy decrease when he uses his left foot, but in most conditions where Rin can get off a shot, it is on target. Rin needs space and range to set up his shooting pattern, the denial of which can result in his shot being off. However, he uses his other weapons to find himself with plenty of both, making him one of the top scorers in Blue Lock.
- Pinpoint High Speed Free Kick: Rin fires a blazing fast free kick, with incredible accuracy. This free kick was so fast and accurate that it went right over Isagi's head, without giving him a chance to react.
- Vertical Spinning Direct Shot: A direct shot from the corner spot, which targets the furthest top corner of the goal. This shot can take players off guard if they do not expect it, thought it can be prevented through positioning.
- Line Drive Shot: Rin attempted to replicate his brother's shot, by dribbling to the byline and using his left foot to fire the ball over the goalkeeper and into the far side netting. However, the decrease in shot power and accuracy meant his shot was saved and hit the post.
- Jump Shot: After feinting to circumvent an opponent's defence, Rin lifts the ball and performs a jumping roundhouse kick. With this technique, Rin is able to both shoot with frightening accuracy and evade a challenge from an opponent.
- Blind Shot: Rin takes advantage of the movements of another player to shield the ball from the keeper's vision, before firing a blind shot that the keeper cannot react to in time.
- Trivela (Shot): A technique wherein which one puts spin on the ball using the outside of their foot. Rin hides his form, to force the assumption that he will shoot with his left foot, before shooting with his right. Rin is able to do this and score from outside the penalty area, as demonstrated against the Japan U-20.
- Trivela (Pass): A technique wherein which one puts spin on the ball using the outside of their foot. Rin can use this technique to pass the ball, manipulating the opponent into thinking his pass has missed, only for it spin back to its destination.
- Oppressive Pass: Rin makes a difficult pass to his teammate in order to continue a play. He will usually play this pass into the optimal space for his teammate to retrieve it and return the pass (in the case of Aryu) or into the space where he expects his teammate to breakthrough (in the case of Bachira). This pass, as opposed to a more creative one, challenges the limitations of Rin's team, forcing them to rise to meet his expectations.
Spatial Awareness: Rin analyzes the entire field, including the positions of himself, his teammates and his opponents, in order to determine the best play. Rin's tactical ability and spatial awareness are at such a level that only Isagi can understand, counter, and rival his analytical ability. Rin is routinely able to predict the positioning and movements of other players, including Isagi, setting up traps and baits to lure them into unfavorable positions, intercepting their plays and setting up his own.
- Spacing: By reading the weapon of his opponent, as well as the positions of other players on the field, Rin spaces himself in such a way as to allow for him to predict and respond to whatever they decide to do.
- Synchronization: Rin is also able to use his spatial awareness defensively, through reading and understanding the core of his opponent's football he can overlap his thoughts with theirs to predict what they will do next. He used this to halt the combined offense of Sae and Shidou during the U-20 match. However, focusing solely on playing defensively makes it difficult for him to join the offense to score his own goals.
Off the Ball Movements: A term used to describe the moments where players are not in possession of the ball. Rin makes use of these movements to position himself in an opponent's blind spot, as well as to manoeuvre into goal scoring positions. He does this after determining the field of view of the players on the pitch, similar to Isagi.
- Positioning: Rin has incredible positioning, constantly moving to areas where he can receive the ball in space and still be able to score a goal. If Rin realises that he will not receive a pass, he always positions himself in a place where he would be able to score if he should receive the ball by chance. He demonstrated this positioning during the Second Selection, as well as during the U-20 match. Rin also uses this defensively, in combination with his spatial awareness. After using his spacing, Rin gives himself enough room to predict where the opponent will likely break through, then uses his positioning to intercept them.
- Super-Speed Interlock: By using the movements of another player as a precursor, Rin moves into a position where he can meet a quick cross in an open space. He used this in conjunction with Bachira to score against the Team World Five.
Puppet-Controlling Soccer: Rin's main play style is about controlling and manipulating what his opponent thinks. After identifying the strengths and weaknesses of each player on the field, Rin uses his superior technique, tactical and physical ability to manipulate them into scenarios that will result in a goal. He can do this by using his own abilities against the opponent, or by combining his strengths with his team's. This style of soccer, pushes his team's abilities to their limits and beyond, resulting in highly complex and effective passages of play that often result in a goal.
- Feints: By positioning himself at a range where he can shoot, Rin manipulates his opponent into thinking he will shoot. This draws in the opponent to attempt a block, before he feints in order to bypass them. Rin can also use this in reverse. By changing his form and hiding his motion he fools his opponent into thinking he won't shoot, before he does.
- Marseille Turn: After manipulating his opponent into thinking he will perform a regular feint, Rin transitions into a roulette, to get around their defence.
- Elastico Nutmeg: Rin knocks the ball sideways with the outside of his foot, in order to force a challenge from his opponent, before using the inside of his foot to push the ball between their legs and get past them. He used this to get past Sendo.
Flow State: Flow, as described by Ego, is the state of "total immersion" or "being in the zone". It is the mental state in which a person performing some activity is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity.
Rin finally reached Flow in the final minutes of the Japan National Representative match. Rin's style of football usually revolves around precisely calculating the weapons of the players on the field and drawing them out to utilise them, manipulating the field for the best way to score. However, when in Flow, rather than bringing out other player's weapons to efficiently utilise them, Rin draws out their weapons in order to shut them down. This usually involves Rin baiting them in some way, to use their strongest weapon, before overcoming them directly. While in Flow, Rin is noted to be several levels above his standard abilities. Rin was able to completely defeat Teppei Neru, Miroku Darai and Kazuma Niou in quick succession, using each of their weapons against them. Even Aiku could not stop him alone but when assisted by Shidou they were able to pressure Rin. Despite this, Rin was able to kick a powerful curve shot that missed only by a couple of inches. Rin is even able to neutralize Sae's dribbling as seen in the last minute of the U-20 Match.
- Opposite Acceleration: When facing someone with speed as their weapon, Rin knocks the ball to the side, in order to bait their acceleration forward, before he suddenly accelerates in the opposite direction, nutmegging them in the process. He used this to get by Neru.
- Off the Ball Movements: When facing someone with off the ball movements as their weapon, Rin will cross them multiple times to get in behind, before using his hand to prevent them from turning around to stop him. He used this to get by Darai.
- Centre of Gravity Full Burst: When facing someone with core strength as their weapon, Rin will force a physical pressure duel, knocking the ball up as bait. When they charge in, Rin will shift to stance with a low centre of gravity, to break their balance, using their own charge against them. He used this to get by Niou.
- (To Ego, Chapter 108) How lukewarm of you Four-Eyes. To me, this match is just..... another stepping stone to becoming the best in the world. 
- (To Isagi, Chapter 44) To me, you're just stepping stones. You guys, and this "Blue Lock" as well. 
- (To Isagi, Chapter 44) If you keep winning, you'll get into Japan's U-20 Team. I'm here to just take advantage of that system. It's all so that I can become Japan's representative and overcome my brother. 
- (To Isagi, Chapter 45) Soccer is a death match. As far as I'm concerned. Just come already so I can kill you. Your lukewarm ball kicking game will end here. 
- (To Team White, Chapter 47) You guys don't learn at all, do you. I'm staking my life on each moment, here. 
- (To Isagi, Chapter 48) How long are you gonna circle theses passes around? And you call yourself a striker? Come. I'll end this. 
- (To Isagi, Chapter 77) Did you really think you could read me? A puppet side-show like you. 
- (To Isagi, Chapter 86) Luck isn't a result of pure coincidence. It's an underlying element of the field that reaches only those who move by their will. If you can't understand that, you've got no right to live in a competitive world. 
- (To Isagi, Chapter 115) Don't get swept away, Isagi. You just have to look at me. In 90 minutes, i'll turn those cheers into screams of anguish.
- The name Rin (凛) means "dignified, severe, frigid and cold".
- Rin's surname Itoshi (糸師) means "thread" (Ito, 糸) and "expert, teacher and master" (shi, 師).
- Itoshi Rin can therefore be interpreted as "dignified puppet master".
- He is the No.1 in Blue Lock.
- He is the center forward for the Blue Lock Eleven.
- He is the captain of the Blue Lock Eleven.
- He is the younger brother of Sae Itoshi.
- He says he doesn't cry.
- His favorite food is ochazuke, especially ochazuke with bream.
- His favorite manga are Dragon Head and Shigatera.
- His favorite animal is the owl.
- His favorite movie is "The Shining".
- He is unfriendly/blunt.
- Rin is fluent in English.
- He spends his holiday either by playing horror video games or immersed himself in horror movies.
- Blue Lock Manga: Chapter 44.
- Blue Lock Manga: Chapter 95.
- Blue Lock Manga: Chapter 108.
- Blue Lock Manga: Chapter 44.
- Blue Lock Manga: Chapter 44.
- Blue Lock Manga: Chapter 45.
- Blue Lock Manga: Chapter 47.
- Blue Lock Manga: Chapter 48.
- Blue Lock Manga: Chapter 77.
- Blue Lock Manga: Chapter 86.