Sukima Suki, Nozoki Ana Recommendations
Peeping is the central theme of both of these titles. Do note however that Nozoki Ana is for adults only, whereas Sukima Suki only features mature themes.
Both main characters are peeping on each other.
In Nozoki Ana it is part of a "rule" between the two, while in Sukima Suki they are unaware that they are both peeping.
Peeping? the two mangas are about peeping into someone, but in Sukima suki, they both peep, but they don't know the other one is peeping, and in Nozoki Ana they have rules about the peep, though Sukima suki is a more light manga, Nozoki Ana is more ecchi.