Responses
This one has characters matching your description and there is a chapter where they visit an aquarium: http://www.mangago.zone/read-manga/eventually_i_will_become_yours/
beta
This one has characters matching your description and there is a chapter where they visit an aquarium: http://www.mangago.zone/read-manga/eventually_i_will_become_yours/
i remember i think they were in high school and they visited an aquarium one of the girls had pink hair and the other girl had black hair