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Kawamura can do it too. Ryoma can only when he knows someone he cares about is losing. Higa members have been doing that in NPoT (mainly towards Kite though). Not really limited to those two :P
Shitenhouji's team do it pretty well. Most of their member are not so serious. Kintarou and Shiraishi can fill that role pretty nicely.
@ Philia: I never thought Sengoku to be a mood changer. If anything he is nothing more than a guy who likes to pick up chicks and he's only 14. Not sure if that's considered a mood maker. I do agree kikumaru is one though.
OK, I give up. I have nothing in Sengoku's favor. But he's still awesome.