Gateways to Casselonia Vol1( Light Novel )

Sorata and his friends are hanging out on campus after school and are excited for the senior class trip the next day, there's just one problem though. Mizuki, the student council vice president, grandaughter of the city mayor, and the girl of Sorata's dreams, injures her wrist as she crashes into Sorata as he and his friends are leaving school, resulting in a fierce confrontation. This ends up ruining the trip for Sorata. On their way to the campsite of the field trip, he gets motion sickness and nearly pukes himself several times while Mizuki tries hiding her injury from everyone else. During the barbecue, Mizuki stains her uniform and as a last resort goes to the nearby lake to wash it off while Sorata goes there to empty his insides. In a twist of fate, Mizuki finds herself drowning and passes out moments before Sorata dives to her rescue. Unfortunately, he also ends up drowning alongside Mizuki the moment his entire body cramps up and thus both descend to the depths, until Sorata regains consciousness and is finally able to break through the surface. He recovers Mizuki's body not far off and realizes she's alive, but when he scans his surroundings, the lake has been turned into a river where crowds of people dressed in medieval clothing are standing near the edges to watch in curiosity, the forest has been replaced with old European style houses of different shapes and sizes. Far off into the distance is a grand waterfall next to a castle tall enough to pierce the heavens. Just what on earth could of happened after they drowned? What is this new fantasy land where they've suddenly appeared? And will they ever be able to return home?