Sazanami Yousuke

After having several setbacks in real life because of his loner nature and holing up in his house, Toudesuke Saionji, a middle-aged man, throws himself into his inventions. Until, one day, he causes an explosion during one of his experiments and ends up reincarnating into another world. Now that Toudesuke has yet to find some way to go back to his old world, will he keep to himself along with Satalia, a vampire girl who adores him, and lead a quiet life where he dedicates his time to his inventions...!?

A tunnel in a mountain that a college student visited with the intention of trying to deliver a video. The giant bugs that appeared there attacked them! VS. Human cruel survival.