Koro Sensei, the titular character from the anime and manga series Assassination Classroom, is a yellow, tentacled creature with a distinct appearance. Due to his unique physiology, it's impossible to definitively say what he looks like under his clothes.
However, we can speculate based on the information provided in the series.
- He is described as being "made of something like a yellow rubbery substance." This suggests that he may not have a traditional skeletal structure or musculature.
- He has a large number of tentacles that are capable of various functions. These tentacles could be his primary means of locomotion and manipulation, making it unlikely that he has arms or legs.
- He is extremely fast and agile. His body must be incredibly flexible and adaptable to allow for such movement.
Ultimately, the appearance of Koro Sensei under his clothes is left to the imagination. He is a fictional character with a unique and fantastical design, and the details of his internal structure are not explicitly revealed in the series.