basically ML has a disease for being rebirth 2 times where all of his organs are experiencing failure (this take place after the xiao family has been dealt and MC decided to stay with ml). MC ask the system for help then tell everything about his transmigration and other world to ML, in where he want MC to go back to his world since he only has a month left. MC then decided to use the system item that give half of his life to ML, but after using the item MC felt no pain. The system completely disappeared after saying it likes having MC as its host.

In the side story the system reincarnated to a cat name er shun (they found it inside ml's orphanage room), both MC and ML are probably going to bring it home.

I still have no Idea what even the xiao family's business is nor have the leads actually communicated

the car accident after ML is "reborn" After which I really felt disappointed because the development up to that event already took ages

• Cannon fodder characters really behave like cannon fodder characters, it's clear to see who you're supposed to side with and who you should find in the wrong / annoying right from the start. Can be a little simplistic and annoying, so if this kind of formulaic writing really bothers you, this may detract from your reading experience.
• In the original plot, "Song Xuanhe" did a lot of really scummy things. As the transmigrator, MC is forced to act out a lot of these scenes, including blackmailing the ML into a relationship and agreeing to "give away" the ML to someone else. While these misunderstandings are resolved in the end, it can be difficult to read about the MC going through these acts.
• As you may have figured out, this novel relies quite a lot on coincidence and misunderstanding, especially at the beginning, when it is walking the tightrope between enmity and attraction between the MC and ML.
• This novel features a fair amount of "face slapping" that some may even call excessive. Personally, I find it a little tiresome to see people crush others through money and status. That's the sort of thing you call scummy when the enemy does it; I'm willing to call it funny the first time, but it doesn't make it better just because the MC does it. That said, it's within a tolerable range, at least for me.
• As with a lot of CN novels, disablement / disfigurement / addiction / etc. Are sometimes used rather lightly as a "just" punishment for villainous characters.

In the previous few chapters, MC shows up to crash his cousin's business launch celebration party, and publicly humiliates his cousin in front of everyone. It's implied that there is a reason, but it's never explained, so all we get is the MC being rude for no reason to someone who's actually reacting reasonably.

MC's cousin gives his 'sad backstory' about being poor compared to MC, and then MC humiliates him for no reason, and this is portrayed as justified. Then right after, MC's cousin is portrayed as engaging in shady behaviour (like maybe he deserved his poor origins??)

a poor waiter who's begging the ML to let him keep his job because the waiter has a sick younger brother that he needs to provide for, and the ML is just standing there with a cold expression and not saying anything. But then in the same scene, it's revealed that the waiter 'didn't apologise properly' and "Simply apologising for ruining someone's clothes really didn't have any sincerity to it. No wonder Xiao Yuanmu (ML) hadn't paid attention to him." The 'proper' behaviour was the waiter bowing ninety degrees (which is practically the most formal bow you can do) and offering to change the ML's clothes for him.

the ML that we've seen fall for MC gets essentially replaced by his reborn version. It resets their relationship almost back to zero, so what was the point of the first 30 chapters then??

ML was reborn 2 times but MC thought ML only reborn once

Rather than being reborn, ML transmigrated from the end of the original book to the current timeline/universe. Pre-rebirth, the CP scenes were so cute and it felt like they were going in the "cold ML softens around the misunderstood MC and dotes on MC until they become coaxed into liking ML too" direction, and I also got attached to that version of ML. Post-rebirth, it turned into enemies-to-lovers instead. There's still sweet CP scenes, but none of the innocent "ML had a hard life but becomes attached to MC after being shown some sweetness" or "ML thinks MC's reactions are cute and ends up spoiling MC" stuff from before! And my sweet pre-rebirth MuMu is gone!! I want justice!!!

Things get very dramatic as the ML's father points out that the MC can't give him an heir and the ML starts disappearing for long periods of time. In fact, the ML doesn't care about the issue of an heir. This is just a red herring by the author. Turns out the ML has come down with a sudden terminal illness that even the system has trouble identifying. The MC and the system are able to save the ML at the last minute with an item from the system store. Supposedly the MC is dividing his soul in half to share with the ML.

I suspect that Z48 instead sacrificed itself to protect his friend. There are a few clues to support this. MC was supposed to experience a lot of pain which does not happen. The words as the system wishes them happiness as it fades away sound very final. A star in the sky goes out, most likely representing the system either leaving injured or being destroyed.

They got together at the end, specifically in Chapter 131. Although it's not literally at the end, it's more leaning towards the end.

Although I was a bit sad to learn that his pre-rebirth self wouldn't be returning, but I also really liked his post-rebirth self.

ML left for America

that part when MC was avoiding being touched after meeting with that actress, and ML deduced that he was probably forcibly touched in the past. Or when MC's cousin locked ML in a room full of snakes.

telling MC that his parents' corpses are on the other side when MC was thinking of staying in that world and telling MC to stay when he wanted to leave