Not only that, why do they all have brown hair? And why does Eito look remarkably like the mc from his prized disciple's webmanga?
Ha, you are right. I totally forgot about Ayato. Maybe they traded designs: Matsuda got to borrow Aria's design for Princess Iriyaa and Matsuena copy&pasted Ayato for Eito. If you add the main characters from Matsuena's Gaiden stories you have enough people for a copy of Osomatsu-san, the name fits as well.