Mutsuhiro Watanabe is a man of many names… and personalities. Known to his family as "Mu-cchan" (4.23.15), to everyone else as the Bird (and a lot of things we can't print here, we're sure), and even sometimes mistranslated as Matsuhiro, Watanabe is the worst of the worst when it comes to abusive prison guards. He makes the creepy guard from The Green Mile seem like a guy you'd love to bring home to dinner.
The Bird gets a few snippets of glowing praise from both Japanese guards and American POWs, like "He did enjoy hurting POWs. […] He was satisfying his sexual desire by hurting them" (4.23.29), and "He was absolutely the most sadistic man I ever met" (4.23.31). Okay, those are more like superlatives than praise, but this bird is more like a vicious hawk than a cute little blue jay, so it only makes sense. In fact, he earns his nickname—the Bird—because it carries "no negative connotation" (4.24.2). Everyone is that afraid of getting on his bad side.
Speaking of his bad side, the Bird is confusingly nice at times, which almost makes him worse. In the middle of beating Louie, he once stops and speaks to him kindly. Louie even thinks, "There was compassion in this man" (4.25.24)… before he gets cracked in the head with a belt buckle again. Forget the Bird's bad side—you don't want to get on any of his sides.
Louie is relieved when the Bird gets kicked out of the Omori prison camp, ordered to leave by Prince Yoshitomo Tokugawa. But Louie's relief is short-lived, and when he arrives at Naoetsu, he's greeted by the Bird. He just can't get away from this dude. (Talk about an albatross… be sure to check out the "Symbols" section for more on this)
Fed up with the abusive treatment, the POWs try to kill the Bird by spiking his food with contaminated stool. He's violently ill, but recovers within two weeks and "take[s] out his rage on the officers and Louie" (4.29.13). It's fun while it lasts (for everyone but the Bird). but his anger is worse than his diarrhea, and when he recovers he makes Louie clean a pig sty with his bare hands, hold a beam for over half an hour, get punched in the face over two hundred times, and threatens to drown him and kill him. He's um… back with a vengeance.
And in short, he's Louie's worst nightmare.
Watanabe vanishes after the atomic bombs are dropped on Hiroshima and Nagasaki, and hides around the Japanese countryside for seven years. He either manages to fake his death, or simply gets lucky that a man who looks just like him commits suicide by jumping off a mountain—he only emerges once the arrest order for war criminals is lifted. He manages to live a nice life after that, proving that real life, unlike fiction, is never fair.
When CBS news uncovers Watanabe's story, he agrees to be interviewed. He seems apologetic in one interview, saying that "war is a crime against humanity" (Epilogue.50), but he doesn't believe he is guilty of any wrongdoing, and in fact says that "beating and kicking were unavoidable" (Epilogue.70) in certain situations. Yikes.
To atone for whatever wrong he thinks he did, he offers to let any of the men he hurt come to Japan and hit him. Hmm, maybe his sexual tastes have changed in old age. No one takes him up on the offer, though, and when Louie tries to meet the Bird, the Bird refuses to meet him. He's flown the coop for good, and no one sees him again.