Ｏｎｌｙ Ｙｏｕ　－世紀末のジュリエット達－

A Japanese teenager named Yuuji is interested in martial arts, and has to take care of his little sister. Their older brother Yuuichi had gone abroad; just when he announced that he was coming back he disappeared under mysterious circumstances. Yuuji and his friends eventually find out that an international supernatural criminal syndicate is in cohorts with an even darker power that is about to bring the apocalypse onto Earth.

[Edited from Moby Games]