WARNING---EASTER EGG SPOILER---WARNING
It is a long katana with a red hilt and a thin, sharp blade. It has a red tint on the blade. It is a cursed blade.
The Murasame will always kill the person who was hit, it will give the enemy a poisonous curse, killing them quickly, so it is a very deadly weapon.
The one issue is that it has a 10% chance of killing the player upon picking up the weapon.
It also has a trump card: sacrificing 80% of Rico's health, it will massively strengthen Rico, making him extremely powerful. The player will suffer a penalty in every way after a minute, signalling the end of the trump card bonus.