I think MC's action is realistic in a certain way. He is too confused to seek revenge straight away, and wants to find the truth first. He is still in te state of denial, not excepting that the girl is a gold digger.
While this manga seems to focus on the "taboo" topic, the content itself is pretty much a normal light-hearted romance manga. Most characters are sane and make logical actions, for good or worse. Not many high stakes going on, and when there is, it will be solved within the next 2 chapters. Not...