Ruby Red wo Kamikudaku

I want to be "special" to my sensei. Akane is an Omega who can see people's pheromones as multicolored "crystals”. During his school days, when he was lonely because of his peculiar constitution, he meets Makise, a school nurse teacher. 5 years later, they are miraculously reunited, but Makise has a secret...? (Source: Libre, translated) Note: Includes one extra chapter.