[Locked] Looking for a School-themed manga

i'm looking for a school-themed manga where a transfer student is too shy to socialize with the new classmates, one of them whants to help by inviting her to come back to school at night and when the two girls enters a room they find all the males of their class naked, the newcomer of course is embarassed but the other girl is already naked and ready to have sex with the boys; in the next chapter they do the same thing at a lake during a school-trip