The Unknown World:For the sake of my sister's soul.

Anime/ Manga series. Hikari Mayumi is a young freshman that has been accepted to one of the top universities in Campbell, she wanted to live a life of a normal freshman, having a part-time job, hanging out with her friends, finding a boyfriend, and graduating. That is her dream. One day as she was living her best dreams, Hikari got a phone call from her parents saying her little sister has gone missing. As the eldest sister, she got to return home and find out what is happening. As she struggles to find out, she encounters a few people who have been in the same situation as her, and she begins to investigate the disappearing high school students, alongside a few friends she encounters. They all set into a dark and ugly truth about the other dimension world. Hikari set her goal to save her sister and the others from the dark place. Her journey might just begin.