Complex sentence: Domon Kasshu is the tough aloof pilot of Neo Japan who was once trained by the great martial artist, Master Asia and earned his master's title of the King of Hearts, having him recognized as the strongest fighter.
Split into simpler sentences: Domon Kasshu is the pilot of Neo Japan who was once trained by the great martial artist, Master Asia. Under his training, Domon Kasshu earned his master's title of the King of Hearts, recognizing him as the strongest fighter.