The guy dressed like a mechanic is the game's main character, Sigma. Sigma is an ordinary college student who will frequently make sexual comments, annoying girls.Fuente
The girl in the center of the character art is Phi. She's cool and intelligent, but will sometimes say stupid jokes. She says she's a C cup when she's actually an A cup.
The story begins when Sigma is kidnapped and awakens in an elevator next to Phi. While Sigma doesn't know Phi, she seems to know him, even calling his name out. A bunny appears on the elevator monitor, causing them to flee the elevator (I'm not sure what the bunny says to make them flee, although if I saw a talking bunny on an elevator monitor I'd flee too). They find themselves in a warehouse alongside seven others. They will have to escape from this facility.
Chunsoft refers to Gyokugen Dasshutsu Adv: Zennin Shiboudes as a "game of betrayal." What that means is unclear at present, as only a few gameplay details have been announced. The game will have visual novel parts and escape parts. The escape parts involve exploring rooms and solving puzzles.
Development on Gyokugen Dasshutsu Adv: Zennin Shiboudes is currently at 50%. Famitsu lists the release time frame as TBA.