Yakuzen Kusuri is Aijou Rentarou's fifth girlfriend. Rentarou first saw her in her teenage form but was unable to stop and meet her despite feeling the soulmate shock. They met properly when he later came to the classroom in search for her, but instead found her in her child form. She is highly proficient in chemistry, able to concoct drugs/medicine with various effects. (Source: 100Kanojo Wiki, edited)