Megami-ryou no Ryoubo-kun.

Synopsis

At the beach Koushi remains confused about Atena. A fish gets stuck in Sutea's swimsuit, causing her to struggle to swim. Koushi rushes to save her but remembering he can't swim sends Kirya instead. Sutea is glad Koushi was worried about her. Koushi sees Atena being harassed by men so he pulls her away, revealing Atena no longer gets nosebleeds around Koushi as he makes her feel safe. Sutea apologises to Kirya and Atena, admitting she was jealous they helped Koushi after losing his home while she couldn't and is convinced Atena has only sisterly feelings for Koushi.

Koushi begins acting strangely. Frey decides cosplay will get him to talk and drags him to her favourite cosplay studio. Frey dresses herself and Koushi as characters from an anime. Tricking Koushi into answering honestly Frey learns most of what occurred during the vacation and his confusion about his current relationships with the girls clashing with his changing emotions. Koushi realizes he wants to protect Atena, but is unsure if he wants to do it as dorm mother, a brother or as a man, but either way he intends to do it with more confidence from now on. He also learns from Frey that she will stop running from her past and someday try to reveal her true blunt self to the Goddess Dormitory.

(Source: Wikipedia)