A massive man with a massive mouth although with not such a massive brain, Tamiya is an honest, somewhat simple, but good man. Extremely passionate about his work and over automobiles, Tamiya spares nothing in his effort to get the best out of everything his auto club does.

Although he seems intimidating (and he is), Tamiya doesn't have a single bad bone in his body. Although he seems to be a little harsh at times, he just likes to follow school (university, more like.) rules by the book. With good intent and a passionate drive, Tamiya doesn't have any bad intents whenever he seems to torture his club, or when he picks on Keiichi all the time. It's his passion for vehicles that drives him to try motivating his club in any way he can so they can accomplish their work with enthusiasm and experience. Dedicated to his club, Tamiya is in search of the ultimate racing machine.

With his apparent childish innocence belying his massive frame, Tamiya may appear rather unappealing to some people. He may even appear fierce and aggressive to others, but in reality he's really friendly and loyal, as well as considerate in his own little way. His demeanour is rough, of course, but he values friendship and has an adorable way of showing affection towards people he *likes*. (Chihiro, anyone?)
Of course, those others he likes such as Keiichi as a good friend and valuable ally, well...... you go figure.

In his last year of N.I.T (I think so), Tamiya also knows how to look for a suitable replacement for him an Ootaki, searching for qualities in that person for which he feels are best for the club. But, we all know Keiichi has all the qualities he needs....
Tamiya may be simple and/or ignorant in some places, but he's deceptively intelligent when it comes to certain things. He knows how to test Keiichi and he and Ootaki even came up with an ingenious way of constructing a cipher using a calculator once. And at least, he's smart enough to know Belldandy's got all the looks their club need for an anchorwoman. ^_^U
Definitely not a man to cross for all his appearances.

Tamiya also likes to choose Keiichi as his club's workhorse. He probably knows Keiichi's one of the most capable people in his club and relies on him to keep things working. After all, Keiichi's always the test driver for all their modified vehicles (Kosuke does include schematics on these too) and their race driver for competitions. Perhaps he's grooming Keiichi to be the next head of the club, or maybe just out of simple hope that Keiichi will somehow accomplish it and will have no bearing on Keiichi's position in the club(?). His belief in being a "man" drives him to try to bring out the "man" in Keiichi and his bunch too, which is probably how he became so massive in the first place.

But all in all, Tamiya is quite a likeable fellow who has no real bad intentions who can be relied on to keep things working. A good leader, passionate worker, and a smart/simple demeanour keep Tamiya interesting and likeable. An honorable man.