The Wallflower is about a girl named Sunako who was called ugly by the first and only person to whom she confessed her love. This incident sparks a life change, and as a result Sunako shuns all forms of beauty, both in herself as well as in life. Concerned by her change for the worst, Sunako's aunt, the owner of a beautiful mansion where four very handsome students live, offers the guys free rent in her mansion if they can turn Sunako into a "perfect lady" (referred to in Japan as the titular Yamato Nadeshiko).
While the four of them manage to make Sunako physically beautiful enough to become a lady, the problem lies with her attitude and interests (which Sunako has no intention of changing). Up until the most recent release in the story, they've managed to convince Sunako's aunt that her niece is indeed a lady befitting the mansion in which they live (and prevent the rent from skyrocketing to triple the required amount). However, in reality Sunako has not changed considerably. Sunako has the tendency to spurt out in a nose bleed when seen by bright creatures, especially around Kyohei.