Tanaka is a really quirky guy. He takes a liking to the protagonist and puts him under his wing. Nothing the protagonist says angers him. Instead, he provides insight to his way of thinking and leaves it at that. 

He is also unusual in that he is probably the only character that does not need the protagonist's support with a problem and comes to his own realizations himself... which is that even though he is a rich and successful businessman who may or may not have shady business practices, he actually enjoys being a mentor for others and watching them succeed. 

It's heavily implied that he grew up poor and has that memory constantly in the back of his mind. It's something to keep in mind when recording his lines. He talks about his success a lot and the ugly nature of business, but the implications are fairly clear that he came from humble beginnings, so he's rather proud of what he's accomplished for himself.