Sudou desired three things: money, power, and Asami Ryuichi... in that order. He grew up poor, but used his good looks to climb the social ladder. Asami took notice of his rapid ascent and thought Suodu's ambitious nature, resourcefulness, and cleverness were qualities that could be useful, so he gave Sudou a position as a fixer- someone who fixes his clients' "troublesome" (read: illegal) problems. In return, Sudou would benefit by receiving "gifts" from grateful clients that could help his way up the social ladder.
The problem occurred when Sudou became greedy and wanted everything NOW. He used his position to take on extremely risky, but immediately more profitable, illegal ventures. Apparently Sudou received a tempting offer to do some work for the politician Kouyama. Kouyama was actively being investigated for embezzlement of public funds (which Sudou didn't know at first), but he was also involved in far worse things- like an East European mob (which we now know is Chernobog). Kouyama wanted to steal Asami's very profitable weapons smuggling route. I don't think Sudou knew in the beginning that Kouyama was working toward Asami's ruin. Then Kouyama discovered he himself was being used as a pawn in a greater game. Instead of him gaining the route, it would be Chernobog. Chernobog pressured Kouyama, who in turn pressured Sudou, into stealing from Asami. Sudou realized he had made a mistake, but he believed he was in too deep at that point to back out.
Mikhail used Sakazaki, who used Mitarai (Akihito's photojournalist colleague), to publicly expose Sudou's connection to Kouyama. This gave Asami warning which spoiled Chernobog's chances of gaining possession of a large weapons shipment. It also killed any possible future Sudou had with working for Asami.
Sudou admired Asami, and at first, only wanted to be acknowledged and to be a part of Asami's inner circle. Eventually he realized he had fallen in love with him. The deeper he got involved with the other group, the farther he was pushed away from Asami. On top of all that, Sudou realized that Akihito, who he thought at first was an insignificant gold digger enjoying his "5 minutes" of being Asami's favorite toy, was actually Asami's treasured lover. The pressure of being forced to betray the one he loved-- who was increasingly regarding him with distaste, and being obvious about loving someone else-- caused Sudou to go over the edge.
Anyway, that's my understanding. Corrections/further insight is encouraged.
Oh, sweet Jesus, thank you.
It seems like it took me forever to understand what happened between Asami and FeiLong (and I'm not totally confidant about that either...), but I was completely lost as to Sudou. Every time he seemed to get upset about Asami, I kept thinking, "You didn't see that coming? This is a surprise to you?!?"
Having it be his own greed that spiraled into something out of his control makes so much sense. I'm in your debt.
Alright, time to reveal myself as a real dumb-ass:
Can anyone help me understand Sudou's story-line? I just reread the entire manga, and I still don't really get it. He has a massive crush on Asami, so he goes behind his back and sells some of Asami's goods to a Russian group? I think? And then seems surprised that Asami doesn't trust him anymore? He attacks Akihito, partly because Akihito exposed him and partly because he's jealous as shit about Akihito's relationship with Asami, and then he's surprised Asami looks at him with disgust? He's surprised when other people have to keep reminding him that Asami is NOT going to save him from the Russians? That Asami has washed his hands of him?
Did I miss something? I kinda get that Sudou is supposed to be a little obsessed with Asami (I think? Right?), but does he really think that he can betray him and hurt his lover and Asami would be fine with that? I must be misunderstanding something...