Pyramid scheme indicates chess pieces:
K-King, Q-Queen, R-Rook, B-Bishop, N-Knight, P-Pawn
http://www.mangago.me/read-manga/koi_to_fukujuu_no_et_cetera/raw/tr_chapter-0.1/pg-7/
AND SOME MORE INFO ON IT IF INTERESTED:
(I used Google translate but as always lots doesn't make any sense, so didn't put all and it might be incorrect)
Anyway in that school are 62 tribes with different qualities. Demons that looks like ordinary human beings with exception of having special abilities.
In the demonic society "family character(?)" and "blood line" is very important for important families, and is customary to strengthen the connection between houses by marriage.
Ability classification system exist in the school and are ranked in 5 ranks with King and Queen as the top (See Pyramid), lowest in rank Pawns can't see what kind of ability others possess.
Individuals born between "Thoroughbred" and "Hybrid" families are called purebred. As a rule, there is an implicit bond that the demon ranked King only interacts with the family in reproduction, and the majority of the demon world is purebred. In rare cases, however, some individuals are born by cross-breeding or interpersonal relationships, and such individuals are called hybrids.
Hybrids often have extraordinary magical powers, however there are also many harmful effects such as "black out" which loses consciousness as a self-defence function when power is exceeded, and depending on the individual, there are cases where loss of reproductive function and loss of life.
reproductive ability is possible even between the same sex, only the inside of the body changes if the conditions are right (Didn't quite understand that last part. Something to do with "Yin")
Koi to Fukujuu no Et Cetera