Bacouple

Kuroi and Shiraishi are known throughout their school as an "idiot couple"—two lovers who are intelligent on their own, but are reduced to plain stupidity in each other's presence. Their tendency to outrageously flirt in public, combined with an extreme lack of awareness of their surroundings, causes an overload of secondhand embarrassment for everyone who is forced to witness it.

However, the couple's actual problem is much more serious: they are so happy that their bodies cannot handle it—so much so that they cannot even hold hands without immediately getting a nosebleed. Despite these complications, the two continue to express their affection in unconventional ways, even if the stress is too much for their poor hearts to manage!