Disclaimer: I own none of the characters and concepts from Dual! Parallel Trouble Adventure, they all belong to AIC/Pioneer and whomever currently holds the license. This fanfiction is not for profit and written for my own entertainment, don't sue me you won't get anything out of it.
Dual! Parallel Trouble Adventure: For Beginners
Dual stared a fairly ordinary Japanese boy named Kazuki Yotsuga, who had the unusual gift, or possibly affliction, to see into a parallel world that was fighting a war using giant robots. Wisely not telling his classmates what he was seeing Kazuki chronicled what he saw as fiction on a website, but he caught the attention of Mitsuki Sanada. Her father Ken Sanada was studying parallel worlds and had even built a device to send someone to one, and wanted Kazuki as a test subject after reading his blog.
An accident threw Kazuki into the parallel world, where he found himself assisting a injured Core Robot pilot, Yayoi Schwael and saving her life. Hastily recruited into the Earth Defense Force he fought the conquest driven RaRa army and their alien based robots, eventually learning the origins of the robot technology. With the aide of the humanoid alien mecha Zinv Kazuki helped end the war and avert a crisis by orderly merging the two parallel worlds. It appeared his adventures were over, until Zinv reappeared....