Sakaeguchi's mother passed away in his second year of middle school. The loss almost made him quit baseball, as he felt there was no point in continuing with out his mother watching him. He decided to continue baseball in high school though when he met Momoe in the summer of his third year.
Sakaeguchi attended the same school as Abe in middle school. Both of them played in the Seniors League, although they were in different classes and teams, Sakaeguchi being in a "weaker" team and Abe in a "stronger" team.
Having such experience, Sakaeguchi is considered to be one of the experienced players in Nishiura High School baseball team. He is exceptionally good at bunting and usually bats second.
Sakaeguchi has short, green-ish brown hair and green-ish blue eyes. He is usually seen in the baseball team's uniform, but outside of the club he wears uniform-like clothes.
Sakaeguchi is a very friendly person, who often tries to set Mihashi at ease. When Abe and Mihashi have trouble understanding each other (due to Abe's short temper as well as his loud manner of speaking and Mihashi's stammering and nervousness) Sakaeguchi generally attempts to mediate, being able to understand both of their mannerisms.
- Initially, Sakaeguchi wears panda-like undershirts (used in middle school) but he later switches to pitch-black version due to the school's recommendation.
- Initially, he takes 40 minutes to get to Nishiura. From his house, he takes 10 minutes to the station via bicycle, rides the train for 15 minutes and finally, walks to school for 15 minutes. Later, he rides his bicycle to school for 20 minutes.
- Under stress, he is known to get diarrhea, a trait revealed to everyone by Abe at the drawings for the Summer Tournament. Abe noticed it during their high school entrance exams.
- He has a crush on Halle Berry.
- On a topic about fantasies, he mentioned that he would be on a luxury liner reserved for just him and the girl and dozing together underneath a parasol.