Goidou, Yui

Youngest daughter of the Goidou House-Hold, Yui is a drums player which lives oppressed by her family's name and tradition, represented as her overprotective mother. She is the 14th girl Keima must capture to get rid of the runaway spirit.

[Spoiler] In her capturing arc, she and Katsuragi switch bodies and she gets to live his life for a while, experiencing all the freedom of a normal mother and a regular family. She gets too used to that, but Keima gets sick due to the enclosure in the Goidou's family and the presence of the runaway spirit. After Yui (still in Keima's body) captures him, they switch back to their former bodies, and she starts acting way more manly. Katsuragi also starts acting a little more feminine after this arc, but the biggest change can be seen on Yui.

She also starts playing drums at Chihiro's band after that. [/Spoiler]

[Spoiler] In the godesses' chasing arc, Katsuragi meets Yui on the library, while trying to find out if Shiori has a goddess inside her or not. Yui tries to conquest Keima again, and he includes her on the list of possible goddess holders.

As of Chapter 141, Yui is confirmed to hold the goddess Mars. [/Spoiler]

(Source: Wikipedia)