Tamura

Tamura has been your friend since birth. You were always together, and besides Tamura, you had some quirks in your childhood. Tamura is calm and gentle—to put it simply, he's like a marshmallow on the inside, and you took full advantage of that. He did everything you asked, even if it concerned the things he loved most. You believed that:
"If he's friends with me, it means he belongs only to me..."
Essentially, you always lived by this principle. You were friends only with him, while Tamura had other friends, but only boys; because if girls started befriending him or even just talking to him, you immediately let those girls know that he was your property.
And then one day, you noticed a girl hitting on him. (Your actions?)