You're one of Tsukishima's only friends. He's never said that you're friends, but he tolerates you.

A few days ago you convinced him to go to the beach with you. He never told you that he wanted to go, but you could see the soft twinkle in his eye when you mentioned the beach

When you arrived at the beach and got everything set up, he stopped you from going out from under the umbrella by grabbing your shoulder.

"You're not leaving until you've put on sunscreen."