Chaos;Gate

Chaos;Gate (also known as ChäoS;Gate) is a Steins;Gate and Chaos;Head crossover light novel featuring two of the titles' main characters.

The story was written by Naotaka Hayashi, the writer behind both the Steins;Gate and Chaos;Head visual novels. It was initially published in the Nitroplus Complete magazine released on September 30, 2009, 15 days prior to the initial release of Steins;Gate.

Summary
The story takes place one year before the events of Steins;Gate. Sena Aoi, while chasing a porter carrying a N.O.Z.O.M.I. Technology terminal in Shibuya, encounters a high school-aged Rintaro Okabe at Shibuya Station. When Sena's calm and composed personality clashes with Rintaro's overtly pompous antics, sparks will fly...