The MC also later has a baby from ML's 'red bead'. Also, towards the end, Zhàn Běitiān (ML) finds a way to turn Mù Yīfān (MC) back to a human with a vaccine. Unfortunately, it brought about a reoccurrence of his bone cancer, so Mù Yīfān ended up dying shortly after their marriage.
After Mù Yīfān's death in the story world, he returns to his 'real world', but Zhàn Běitiān--with his spatial abilities--finds a way to cultivate and cross the worlds to Mù Yīfān's real world. He ends up being 'reborn' without his alternate world memories in the original Zhàn Běitiān. Later on, after protecting Mù Yīfān from a car, Zhàn Běitiān ends up in a coma where he gets his memories back. There's a bit of drama with the MC thinking his sister and Zhàn Běitiān were engaged, but it turned out to be a fake engagement. It turned out that the original Zhàn Běitiān and the story Zhàn Běitiān were the same, and both loved the MC. The MC actually subconsciously also always admired/loved the ML, but never fully realized it until entering the story world, due to their past rivalry. Zhàn Běitiān helps the MC avoid any drama by paving the way for their families to accept each other. The ending is super, super sweet and romantic.
Also, I didn't summarize the 'ending' in the story world since the fighting and plotting is pretty large-scale, and it would take many paragraphs to describe. Just trust that it's very awesome.
Mu Mu turns out to be a Silver vine plant spirit (Actinidia polygama) that is known to elicit euphoric response in cats.... This is why the ending is smutty...
Any time the main character attempts to resist in any way against the him, Shiori essentially forced into s*xual submission and emotional abuse/manipulation. Regardless of whatever justification in the plot the author wrote for his behavior (which is barely any), it's a stretch of belief that they could have a supposed happy ending.
Supposedly, everything the Kurosaki did was 'justified' in the Shiori's eyes somehow, wrapped up in Chapter 7.