Houkago Adventure Valiant

Daiki Okuma, while he's trying to confess his love to his beautiful schoolmate Mami Fukuzawa, sees a dimensional passage opening in front of his eyes, from which arrive a girl and a monster that, while fighting, hurt Mari. The mysterious girl, Selphy, tells Daiki that the only way to save Mari is to take her on the other side of the portal.

(Source: MU)