With the Dark Tournament far behind them, the gang is in a whole new mess! Someone is trying to pick up where Sakyo's dream of opening a portal from the demon plane into the human world left off. Already, energy from their evil world is seeping through. The group heads to Swarm City and finds the place crawling with nasty insects only those with a developed sixth sense can see.

Yusuke and friends wind up in the hospital, hot on the trail of an evil doctor who uses demonic bugs to spread his disease. It's a race against time with an entire hospital of people's lives on the line!