I know this one I'll have a look for you
Smells Like Green Spirit
Hitomi No Giwaku
Hikari to Yami no Logic
Chikan Diary
Karada Meate De Warui Ka
Stupid Story
Maid in Prince
Katekyo!
Kouya no Seifukuou
Faraway Tears - Blue Grey Dream
These are the only ones I can remember with people with purple hair on the front hope it's one of them
Thank you so much for your help and the time you wasted to check this ><
But unfortunatly it's not one of these manga
The uke has long hair I did not specify it sorry and he is always dressed as a girl so I tought it was a shojo XD
It's ok and I hope you find it when you find it can you tell me what it is called I'd appreciate it
Sadly his hair is not purple, but maybe this is the one you're looking for?
http://www.mangago.me/read-manga/hanayome_wa_juunanasai/
It's not this one but thank you
I finally found it omg ><
https://myreadingmanga.info/miyashita-kitsune-saku-no-kono-hana-eng/
I search a yaoi about cross dressing. If I remember well the uke (the one who is dress as a girl) has purple and long and wavy hair, I know that because it's on the cover. The couple is very lovey dovey, they love each other so much. They are high schooler. And I think they do sex outside >w<
It's a OS I think.
That's all, good luck to find that ^^"