And the Enemy into the World

Since her dad's death since elementary school, Kamura has taken the role of being the responsible one in the family, including cooking, cleaning, and simply even getting her mom up for work, whom she promised to always protect. But then her mom tells her that she is getting remarried, and finds out about her soon-to-be 2 years older brother-in-law who she just saw homeless on the streets the day before! And now her friend Youhei, who always teases and makes her feel like a fool, is acting differently...and even tries to comfort her?! Will Kamura be to able accept her new family life with a father and brother, and be able to let go of her feelings of being responsible for her mother?