it's not really bending, it's just the angle. a lot of artist that draw Katana's make it have a curved angle like that when being brought to the eye like that.
A sickle is for harvesting and is sharpened on the inside curve. This looks like a scimitar, but other pics of Tomoe reveal it as a katana. The pronounced curve is a product of artistic license, but yeah--it does make it look extremely flexible. Perhaps it's forged from spaghetti.
