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Souma Hiroomi is the assistant chef who works at Wagnaria. Technically, he's supposed to be the co-chef, but since he doesn't do any work, he isn't concidered a full chef, just an assistant chef.
Souma often gets out of doing work by threatening everyone with their dirty little secrets until they do what he says. Souma, behind his cheery face, is actually a master secret finder. Just by knowing someone for a day, he can already discover a deep, dark secret about them. He does this by using tricky word-play to force it out of them, or by digging around to find the information. Thanks to this, he now has dirt on everyone in Wagnaria except Yamada and Kyouko.
The first evidence of this was shown in episode 4 when Souma dug around in the trash and found an old picture of Takanashi dressed as a girl since he could only get hand-me-downs from his sisters. Souma then cheerily threatened to expose the picture to everyone if he didn't do what he said in the future. Takanashi had no other choice but to obey Souma's every command.
Souma has been seen threatening many of the employees throughout the series. Whenever someone reminds him about his work, Souma will gently start to remind them about their dirty little secret, but before he can finish, they quickly say that they'll do his work before running off. Takanashi has seen this many times before and is still amazed by it.
The one person who has actually found Souma's weakness is Yamada. When Yamada wanted to find out about him, she started to ask around, but ended up finding out that no one knows anything about Souma. This is because Souma keeps as quiet as possible about his personal life so no one could ever use one of his secrets against him. However, Yamada used this has Souma's weakness and started crying in front of him, saying that she felt sad that no one knew about him. As Souma, flustered, tried to calm her down, Taneshima walked into the hall to see this scene. Taneshima misunderstood the scene and thought that Souma was bullying Yamada. Taneshima then changed her opinion on Souma and now thinks he's a heartless, scary bully. Souma was mortified at the fact that someone had found his weakness. However, thankfully, Yamada soon grew to love Souma and now they can be seen hanging out with each other a lot and they even do episode recaps together.
Souma often goes out of his way to get into the personal lives of others. The one life he is most interested in is Satou's, preferrably, Satou's love life. Souma loves thinking of new ways to get Yachiyo to notice Satou, however, they always fail miserably. He has told Yachiyo many times to think more about Satou, but she always misunderstands and thinks that she should only think of him as a friend. Interfering in Satou's love life angers Satou, and he often beats Souma with a pan for trying to do something to it, but Souma only has good intentions, and he knows that he should never tell Yachiyo point-blank that Satou loves her. This shows that Satou and Souma have a trusted friendship and that Souma knows right from wrong.
Another reason why Souma likes to find out secrets because he thinks it's very exciting to reveal them. He has tried to rope Takanashi into revealing them with him several times, but Takanashi never goes along with it.