one in the Vanilla's room.
one in the north cooridoor
one in the med lab
one on the windmill (before the training rooms)

one on resort planet
one on ocean
one on ancient
and one on Cockadoodle

Unfortuely i found them and when i talked to the girl again she ask me to find 8 again donno Why

that's prolly because you missed:
the lamp in the bedroom
a second one on ancient planet
the 'X' in 'exit' on the angel room floor
dunno the other 5 though...

there's one in all of the bedrooms

one is in the kitchen, its the mug

Here's the list of screens where i've found secrets. But first make Mint your slave.

Angel room
Forte's room
Hologram room
Kitchen
Medical center
Milfeulle's room
Vanilla's room
Your room
[Ancient Planet] Information Room
[Ancient Planet] Outside Building
[Area Enigma] Outside School
[Area Enigma] Town East
[Chickleen] Forest East
[Chickleen] Landing Site
[Cockadoodle] Theme Park North
[Cockadoodle] Theme Park South
[Jungle Planet] Landing Site
[Ocean Planet] Inside Resort
[Ocean Planet] Island Beach
[Resort Planet] Town Area

How to go to other planet or.... How to go out on Angel base?