This is a mixed martial arts fighting manga about the Miyazawa school of martial arts. Initially, it is about Kiichi trying to heal his father after he was nearly killed by his brother Kiryu. But then it goes on to be less about that as his father recovers and some tournament style fighting begins. At that point various apparently overwhelming opponents will encounter Kiichi on his way to the top. The objectives of the various characters start to play a more and more important role, as well as the different philosophical projections of several martial arts and disciplines.
Tough is a completed manga by Saruwatari Tetsuya, first published in 2003. It blends thriller, action, psychological and crime. You can read all 437 available chapters of Tough online for free on MangaPulse; the newest is Chapter 426, added 2018-03-10. The series is finished, so you can read it from start to end in one go.