I haven't read either of these two in several years, so my mind is a little fuzzy over the details, but any ideas are welcome of course.

Manga #1 - it involved a female mc who was the daughter of a fish merchant (?) And the male mc was a merman (?)

Manga #2 - involves a female mc that has no memories of her past, but ends up in a school where there are 2 different types of students. Something about a master and pet (?) Type relationship. I think the pet or whatever they were, were stored in earrings or something, because I remember her losing an earring and someone else finding it, and there was a guy in it... sorry if this one was very vague

Manga #2 sounds like Mitsu x Mitsu Drops / Honey X Honey Drops

Quote from hoanghaigoldsea

Manga #2 sounds like Mitsu x Mitsu Drops / Honey X Honey Drops

It's not that one. The female MC has no memories of her past or anything, but yet she lives in a very nice place with... I think maids... that take care of her... it's like she has a hidden benefactor or something. I didn't get to read much into it sadly.

Edit: I have found the title of the second manga. 🙂 🙂 It's called Tiara.