Fun fact : scythe are actually the worst design a bladed weapon can be. Terribly unwieldy for one, and you need to make big, predictable and easily to dodge swing to use it.
That girl falling in love with the MC is not completely out of nowhere. He is kind of a good catch. You see some really stupid reason for falling in love with a beta MC in most Japanese harem manga but I don't think this one is bad.
And I don't think him hiding a fiancee is stupid. It's not...