Yaku Yakuzen

Yakuzen Yaku is a main character and is Rentarou's 16th girlfriend. She is the grandmother of Yakuzen Kusuri. Yaku has a similar appearance to her granddaughter, Kusuri, but due to the strength of her granddaughter's immortality drug prototype, her appearance is not reverted by the neutralization drug. She has turquoise eyes and long, straight red hair. However, her bangs are much more well-kept, and she has a smaller ahoge. She wears a traditional kimono and wooden sandals. When Yaku was young and still an active military medic, she wore a light-colored shirt, white medical coat, light-colored trousers, and boots and carried a medical kit. Yaku comes off as a calmer and more mature version of Kusuri. She tends to act rather grandmotherly towards the others and seems to enjoy the youthful antics of the younger members of the family. She also is rather coy and tends to tease Rentarou. Yaku is also technologically illiterate and easily confused by modern technology. She refers to smartphones as planks, and buttons as peony flowers. She also seems to be afraid of cars. Like her granddaughter, she ends her sentences with "-nanoja" ("yes, yes" in the official translation), a more antiquated version.