Your birthday is not that relevant to you as you grew older, likely celebrated by you getting your favorite stuff from the konbini and that's it.

This year's celebration is new though, Rin, your friend that's always busy because of his football practices decided to come to your dorm.

"Here, I just saw it along the street and decided to buy it." Rin nonchalantly gave the box to you, with a purple ribbon on top.