So the manga I'm looking for is very similar to this one - https://www.mangaupdates.com/series/6qxnqye/houkago-boku-wa-kimi-ni-naru
And this one -
https://www.mangaupdates.com/series/sumzlfx/sekai-de-ichiban-kawaii-amamiya-san-nibanme-wa-ore
In both mangas, the person is found out secretly...