Tamotsu Mikogami is the father of the Mikogami sisters—Riko, Rimu, and Nagisa—and the husband of Haruka Mikogami. He works as a high school biology teacher in Kamihama, specializing in microbiology with an obsessive research focus on water fleas. This obsession leads him to prioritize hunting for specimens even during family vacations. His enthusiasm manifests in fanatical behavior when discussing the subject.

At home, Tamotsu displays a generally relaxed, permissive, and easygoing demeanor toward his daughters. He appears somewhat absent-minded and clueless, showing no awareness of their activities as animal detectives or their special abilities. However, he becomes uncharacteristically sensitive and vigilant about their romantic interests, reacting strongly to hints of dating and even spying on them. Tamotsu is also depicted as gullible and trusting, yet inherently courteous.

Tamotsu's past holds a significant connection to the antagonist Kyousuke Futatsugi. Years earlier, Futatsugi entrusted Tamotsu with delivering a love letter to Haruka, but Tamotsu forgot to include Futatsugi's name. This oversight contributed to Haruka marrying Tamotsu instead, fueling Futatsugi's enduring resentment. Tamotsu is the son-in-law of Yuuki Mikogami, who was transformed into a turtle. Tamotsu collaborated with Yuuki and Haruka before Futatsugi's interference complicated their work.

His role in the narrative stems primarily from his relationship with Haruka, which acts as a catalyst for Futatsugi's antagonism. Despite limited direct plot involvement, his past forgetfulness and the unresolved conflict indirectly influence broader events.