What Should I Do About My Boyfriend's Love-Brain?

After the man I fell in love with at first sight rejected me without the slightest mercy, I spent the night sobbing and drinking, mourning the first love that had ended before it even began. Then I ran into the very man who had rejected me. He had completely changed from his cold attitude earlier that day. His expression was full of concern and a tenderness that seemed to come from nowhere. He sincerely apologized and told me that a slug had kicked his brain out of whack that morning, and that he had only just recovered. Me: ? That's really not necessary. Also, what kind of slug can kick someone? He politely asked if he could have another chance to pursue me. Utterly confused, I turned him down. It's not that I could immediately become indifferent to a face so stunningly beautiful, but I really couldn't accept that my future boyfriend might have a split personality, going from gentle and warm one second to treating me like I didn't exist the next. He listened seriously to my reasons for rejecting him, then calmly told me it was a minor issue. He just needed to brainwash his other self. Me: ??? * 1. Bungou Stray Dogs only, pairing is Boss Dazai. Includes a love triangle between different Dazais. 2. A wish-fulfillment story, very sweet and slice-of-life. 3. The events in the blurb happen because one Dazai transmigrates into another Dazai's body (doge). One of the male leads gives himself away from the start. 4. OOC warning, tons of headcanons, heavily altered plot. 5. It's so itchy, my lovesick brain is growing in. I need to write a sweet romance to cheer myself up. 6. Blurb written on 2023.06.26 and saved as a screenshot. Premise: Only by learning to love yourself can you better learn how to love others.