Inside this giant mouth is a person, trapped, because they're a criminal. They did something bad (they touched the mouth of another person without consent) and now they're in mouth jail for criminals.
The criminal is only wearing shoes (しゅう). They're completely naked otherwise. They have to wear shoes because the mouth jail would be too slippery for them to stand otherwise.
Currently there are no similar looking kanji which exist in the WaniKani learning system