Koizumi Marine
小泉 鞠音
| Koizumi Marine小泉 鞠音 | |
| Aliases | Mari-pon |
| Hair | Pink, Shoulder-length, Sidehair, Twin Tails |
| Eyes | Pink, Tareme |
| Body | Pale, Slim, Teen |
| Clothes | Rubber Band With Beads, School Uniform, String Ribbon Tie |
| Role | Kouhai, School Swimming Club Member, Tenth Grader, Younger Sister |
| Visual novels | Side character - Cosmos no Sora ni |
DescriptionYounger sister of Hiyori and one of the members of swimming club. | |