The first in a trilogy of dungeon crawling RPGs for the PC. Create and customize a team of 6 people from 16 classes to try and survive the Abyss. The save file from the first game can be used in the second.

The games were not originally released outside of Japan but a fan translation was made for Code Hazard.

The first and second game were later re-released on the Playstation Vita in Japan under the name "Tokyo Shinseiroku: Operation Abyss" in 2014 and in North America and Europe under the name "Operation Abyss: New Tokyo Legacy" in 2015.

From the wikia:

"The setting in near future Tokyo, where monsters known as malforms keep the city under constant threat, and portals that lead to a mysterious dimension known as the Abyss have emerged. To investigate these mysterious phenomena, the government has established a special agency: the Contemporary Physics Organization. Players join the X-Force, a unique group of teenagers modified by the CPO Code technology."