Although they attend the same school (and year), Kosei and Tsuyu do not directly interact until the Joint Battles, sets of 4 v 4 fights between classes A and B, with the addition of general studies student Hitoshi. The battles play out with the teams competing to capture their opposers while evading capture themselves. For her Joint Battle, Tsuyu is teamed with Eijiro, Denki, Koji and Hitoshi. Kosei competes on the team opposing hers, and his team consists of Ibara, Jurota and Hiryu. It is notable to mention that the fight centered around the team effort that went to fighting against Jurota, rather than Tsuyu or Kosei’s endeavors.
Midway through the fight, Denki is captured by Jurota in his enlarged Beast-Mode. In an attempt to get Jurota to drop him/loosen his grip, Denki shoots out a full bodied electrical charge. Kosei, who’s previously been standing atop Jurota’s back launched himself upward to escape Denki’ shock, but Tsuyu takes this opportunity to capture him with her lengthy, frog-like tongue. She’s shown carrying him to the designated capture zone. Her tongue is wrapped fully around his body in a humorous manner. After she drops him off at the ‘jail’ and secures him, Tsuyu leaves Kosei to brood. Kosei sits, knees to his chest, and muttering to himself. He says “They might’ve for me but…” he trails off, and brings a hand to his mouth and now blushing face. “… Her tongue…!!” (the scene shows a flashback of Tsuyu carrying Kosei; “shoujo bubbles” are used; these “bubbles” are only used to convey romance within the series.)
After the fight reaches completion, the two are not shown to interact further. Aside from this brief interaction, as stated earlier, Tsuyu and Kosei have not, and do not interact, although they can both be inferred to have at least been aware of each other’s existence as early as the events of the Sports Festival (The students of the hero course all fought alongside/against themselves).
Alongside AwaMomo, TsubAsui is one of the few inter-class relationships to make slight prominence within the series, given the lack of shared appearances between the classes (A & B). Kosei does not have all too many ships for himself, being such a minor character, but Tsuyu has the popularized TokoTsuyu and TsuChako for herself. Regardless, even the slightest hint of a potential future romance within the series does not go unmissed by fans, and many have found themselves to enjoy this unexpected ‘rare-pair’.
The brief carry scene is occasionally one argued over, as some choose to believe it lacked romantic significance. The reason being that it seemed Kosei’s thoughts were more of Tsuyu’s tongue and it’s apparent lewd capabilities, and not about an actual crush/feelings for Tsuyu herself. However, the appearance of the well-known pink “shojo bubbles” in the scene give another thought; these “bubbles” have only been used in blushing moments between Izuku and Ochako before the scene, so it is notable to consider their appearance even so.
- Tsuyu and Kosei share the physical trait of “wonky” eyes, with big, round pupils in a less humanoid shape than seen as usually seen.