Orizuka Momoko is a regular supporting cast member of the anime and manga series Umisho. For much of the series, she is the high school's swim team captain. The most serious and sober-minded of the bunch, she often finds, to her mind, she is surrounded by fools and slackers, but also tries her best to be a friendly sort, and on occasion, a good sport as well. When a potential embarrassing situation comes the team's way, it is even money whether it will strike her or her friend and ally, Okiura Kaname. It is Orizuka who sees the swim-team potential in the quirky Ninagawa Amuro, though bringing it to life is a major headache for her, as are the antics of the team's unabashed male perverts, Takeda and Ikamasa. It is difficult to say whether an attraction exists between Orizuka and Kaname. If there is, it remains mostly unspoken, only coming out in odd or awkward situations. Each seems to know the other is a good deal more reliable and stable than most of their teammates, and in a team like theirs, perhaps that is enough. Her relationship with Ikamasa is similar but a bit more strained, with his outlandish antics and over-the-top perverted attitude making him a real pain. Despite this, they are friends on some level, and Orizuka respects his swimming ability.
When Ikamasa and Orizuka graduate and must leave the team, they maintain an advisory role, with Orizuka's tough-love approach finally forcing Kaname to learn how to swim, and encouraging him to become team captain in her place. She also teases him about his developing relationship with Amuro, and aids the team in training both for tournaments and to build the future members of the team. In the end, she becomes a teacher herself, frequenting the bar now owned by Ikamasa, where she now complains about her students instead of her swim team.