In 2063, MegaCorp GENEAR conducts gene experiments, while supposed restricting human cloning. While trying to escape from the North European GENEAR facility with a mysterious stone in his possession, genetic test subject No.13 gets into a fight with one of the facility's higher-ups and gets defeated. Finding himself in a sewer, he realises that he's suffering from Laser-Guided Amnesia and starts a quest to discover who he is while entering the facility. Once there, he meets a lab worker, Sarisa Stingray, who's only there because of her missing sister Alissa, and the two form an alliance.
A unique element in the game is the use of biochips - the player can collect different kinds of chips, such as applying a 'Speed' one to go faster, or 'HP' to get more health. Mix them up to create certain abilities, such as smoke bombs, dashing and climbing. Also, they're able to drop bombs from No.13's right arm.
Tropes that apply to this game include:
- All There in the Manual: The game's manual reveals some background information on the characters, such as Alissa being a former gymnast.
- And Now for Someone Completely Different: After No.13 is drugged and unable to move, you take control of Sarisa, armed with a gun in place of bombs, and have to create the reversal for the drug.
- Big Bad: Gread.
- Big Creepy Crawly: The Snow Worm boss. It can only be defeated by planting bombs on where it will pop up, leading it to accidentally eat the bomb and suffer internal damage.
- Cel Shading: The game's graphics are cel-shaded, giving it a manga/anime look.
- Forced Tutorial: After the Hopeless Boss Fight with Gread, the player experiences a tutorial of how to use No.13's bomb and biochip abilities. Justified since it's a Flashback No.13 has after getting knocked out.
- Hopeless Boss Fight: At the start of the game, you fight the boss Gread. You have to lose in order for No. 13 to wind up in the sewers and start the main events of the game.
- Laser-Guided Amnesia: To No.13.
- Meaningful Name: Gread.
- Morally Ambiguous Doctorate: Dr Craid - he's perfectly willing to experiment on humans, even if it means that they'll be in pain.
- The Reveal:
- It turns that Sarisa's sister was being experimented on by GENEAR all this time.
- No. 13 regains his memory and discovers that he barely had any memories before waking in the sewers, as he's a clone.
- Sequel Hook: In The Stinger, Dr Craid is revealed to be alive and well, escaping from the facility in a helicopter, and now possesses enough data to start his genetic experiments all over again.
- You Have Outlived Your Usefulness: Gread shoots Dr Craid and leaves him for dead after witnessing how powerful No.13 is.
