Description From Hau~ Omochikaeri! copy and pasted from vndb
A great disaster will befall the island nation of Grande Yakumo on its 1000th anniversary. A large tectonic shift caused a giant relic structure to suddenly appear out of the ground. After a difficult journey, an investigation team arrived at the ‘first room’, where they found Akira in a cold sleep. They wondered if he could offer a hint about the pre-collapse era, but no one knew if he was alive or how they could wake him up.
One day, three friends Himari, Fiora and Luka snuck into the research lab where Akira was being held to take a look at him. Suddenly, there was a large quake and the princess Himari accidentally kissed him. Her kiss woke him up, just like in Sleeping Beauty except with a reversal of roles. Later, they found out that when he fell asleep, someone must kiss him to wake him up. Since Akira was essential to the search of the ruins and understanding what caused the collapse of the previous world, the three girls were also brought along to give him kisses.