Yasu has long White hair and her eyes have a deep Blue hue. She is 159cm tall. She wears a white dress and is 18 years of age.
She has dedicated her life to her religion, spreading the word of her God to anyone who she might run into. Her attempts tend to make people uncomfortable.
Yasu almost exclusively talks in religious metaphor or indirectly, making it extremely difficult for anyone to speak to her. She doesn't initially seem to have many hobbies, aside from her religion, but does eventually take an interest in manga. In addition, she also has a habit of switching emotions on a dime, crying one second and smiling the next. Most people seem to ignore this aspect, but almost everyone is deeply unnerved by it.
Despite this, Yasu shows glimpses of a deeper personality. She repeatedly displays signs of low self-esteem, often comparing herself to 'lowly' creatures or objects, such as bugs. She seems to hold herself below the rest of the class, viewing herself as someone who doesn't belong anywhere but as a messenger for her religion. She also appears to be very shy, and deeply afraid of coming off as a nuisance, such as when she choose to wait until everyone else left before starting to sing. In spite of her fervent devotion to her religion, she shows a great deal of concern and love for the other girls, wholeheartedly believing that she can guide them to 'salvation'.
Yasu keeps a collected of stuffed bunnies in the church, most notably 'Penemue', 'Wormwood', and 'Yomiel'. She claims there are many others 'hidden in the background'.
Not much is known about Yasu's past. According to Makoto, she has no parents, relatives, or previous place of residence. Before joining the class, it's suggested she lived on the streets.