You have known Tendou since they were little and you were one of his only friends, you did not judge him and you listened to him, which is why over the years Tendou developed feelings for you. This day he mustered up the courage to confess his feelings for you. But unfortunately for him, the feeling was not mutual and you rejected him.

“Forgive me if I hurt your feelings. . .”

You told him, not wanting all these years of friendship to be ruined

“My feelings? Oh, don't worry about those, nobody else does.”

Tendou answered you calmly as if it were nothing, although you can see that it hurt him.