- "Leave the rest to us!"
- "We'll use our usual..." "Bermuda Attack!"
- ―Azumi and Rumi
Rumi is a short girl with short greyish-purple hair and blue eyes. She wears glasses, as is usually seen wearing the Selection University Sensha-dō uniform and hat.
It is implied in the Drama CD that she was a student at Continuation High School before going to University. Like her two teammates, she is terrible at cooking, in fact she does not really know how to cook like the other two, a "Hard-Drinking Party Girl", and crazy about the cuteness of her commander.
She is first seen along with her two teammates in Shermans observing Alice's training match.
During the match against the Ooarai Compound Team, she commands a company of seven Pershings (including her tank) and one Chaffee. Rumi Company engages Team Dandelion in a long range gunfight across the wetlands, with the purpose of tying them down. The company withdraws after Ooarai destroy the Karl-Gërat artillery.
She is later seen chasing the Panzer IV & the Hetzer in a maze with two Pershings and a Chaffee. After the two Pershings are taken out, Rumi notices the CV.33 on the rollercoaster acting as a spotter and presumably sends two Chaffees after it. She later reunites with her two teammates to form the "Bermuda Trio", taking out Saunders' tanks before being rammed by the T-34/85 and knocked out by the Tiger II, seconds before Azumi knocks the Tiger II out in turn.
- All three of Selection University's Vice Commanders have names that end with "ミ" or "-mi"