Before Yoshida Haruyuki drew a story about anthropomorphised blood cells battling against infecting microorganisms, this series focuses on personified "good bacteria" and "bad bacteria" waging war in the intestines in Hataraku Saikin the shoujo spin off to the award wining Hataraku Saibou manga he drew a story about two twins, a boy and girl both named Tama (written with different kanji). Both are table tennis prodigies, but the sister quits table tennis before finishing elementary school, and becomes engrossed in other hobbies. However, the brother continues and becomes a champion even in elementary school. While the brother aims to go to a middle school with a good table tennis program, he becomes sick and is hospitalized and cannot play. To preserve her brother's dream, the sister decides to enroll in the school and take her brother's place until he can recover.