Yusa is a girl with long blond hair tied into two pigtails secured in place by a red ribbon each. Just like most of the members of the SSS, Yusa wears the standard uniform of the group. She also wears brown stockings and black loafers.
She is also seen wearing an earpiece with a microphone attached to it or carrying a walkie-talkie.
Yusa is an observer during the missions and her ability is transmitting information to help her team. She is a calm and gentle mannered girl. She also has a straight-forward and tsukkomi character. She doesn't show any emotion, and called scary by Hinata and Otonashi (in an omake). She also can't calm down without her headphone.
When the Battlefront first met Yusa in the manga, she was brutal, slightly unstable and had a strong hatred against boys and men. She tried killing NPC males but wasn't satisfied since they just kept on re-spawning. When she saw the SSS, she saw it as a chance to kill off living males for good, though was disappointed with the fact that they too couldn't die.
Not much is known about her past; and how she died, when she ended up in the Afterlife, or what her regret remains a mystery. However, given the fact that she has a strong hatred against men and will brutally murder them shows that she may have been physically or sexually abused by them, a possible clue to her suffering and regret.
It is revealed in Chapter 32 of Heaven's Door that her emotionless personality is a result of using the Angel Player program through the help of Kanade to seal away her violent side. While succeeding in their goal, due to the system Kanade programmed being incomplete, as collateral damage all of Yusa's emotions were sealed.