From Futekiya:

The handsome, popular Mihiro is used to being the target of girls looking to ask him out. Still, as he begins to get fed up with shallow confessions of love from girls who don’t even know him, he also finds himself being drawn to Tsumugi, his classmate whose hobby is peacefully watching birds. Tsumugi’s favorite bird is the swallow, and he comforts Mihiro by telling him that even female swallows identify the most healthy male birds by their looks because it’s a hint at how beautiful they are inside, too. For the first time, Mihiro feels a bit happy being complimented like this and begins to tease and pursue Tsumugi in return.