Tbh if we go by the hair trend, the tower master is unlikely to be the true ML. It's just very rare for people of similar hair colours get together in these, stories, never mind people who have the same hair colour (both are blonde)
My bets are on the CP and merchant. The merchant would be interesting just for a difference in character style (personality + dresses completely different to other characters), but according to the summary, he treats Erne/the body MC possessed like a child. I see it difficult to change that, so my biggest bet currently is towards the CP. Will have to wait until we get to meet all the ML candidates and how MC interacts with them before I have more sure of an opinion ╮(￣▽￣)╭
Spoiler
Yes CP is ML. Called it from miles ago. So this is just another typical reincarnation. Not worth it
Noo the red hair was better!!
My favourite is the merchant head cause literally, just looks at that masterpiece of a man. But I bet the ML is the CP or the Tower lead. Ugh but I love long haired men