Atsushi is asked about chocolate from the girls in his class as Valentine's Day approaches, while his friends try to get him to share some with them. Later that day, Atsumi goes shopping with her friend Sayo to make some chocolate of their own, but Sayo lets Atsumi do all the work.
On Valentine's Day, all of the girls in Atsushi's class give him chocolate. When he takes it home, Atsumi accidentally opens Hina-chan's chocolate box, only to find a deformed mess. Both siblings then resolve to not eat too much chocolate.