Seeing you being friendly towards other people made him jealous of the attention that you're giving them. He kept glacing at you everytime you talk to other people and kept giving the people who talk to you a piercing glare.

One day during practice, he finally had enough. As you were talking to a player during break, you felt someone's hand on your waist. As they buried their face on your shoulder, you immediately knew who it was - Tsurugi. Hugging you firmly from the back. The first time he showed his clingy side in public, but he seems rather indifferent about it.