Alright so this is more of a personal note than anything, but the order of when the men came to the mansion is:
1.) Obviously Comte goes first since in Leonardo's "The Day that he Came to the Mansion"/TDTHCTTM, it's said that Comte is the one who had it built in the first place
2.) Shakespeare is next, since in Leo's TDTHCTTM, he's there before Leo even arrives
3.) Leonardo is third, since as once again seen in his TDTHCTTM and also just in various other routes, him, Comte, and Will were there for some time before the others came along
4.) In Vincent's TDTHCTTM, there's only Leo and Comte present, and there's no mention of anyone else living there, since Will would've already moved out by this time. Since there's no one else here, I think Vincent goes here
5.) In Theo's TDTHCTTM, there's no one else there but Vincent and Comte (and presumably Leo as stated previously), and Comte only says "there's SOMEONE I want you to meet", not multiple people. So I think Theo and Vincent were actually some of the first residents to be chosen
6.) Now, there's no TDTHCTTM for Dazai, but in Arthur's TDTHCTTM, there are only Comte, Leo, Vincent, Theo, and Dazai in the mansion, so he must go here
7.) Theo says that Arthur came to the mansion a few years after him, so they're actually more spaced out than I thought. Anyway, as stated previously, Arthur HAS to go here since he's the next resident after everyone I previously listed as seen in his TDTHCTTM. Not much to say about this one, he just goes here
8.) In Isaac's TDTHCTTM, both Arthur and Dazai are present. Other than that, his presumably has all the characters I previously stated, but Sebastian is not present. Mozart's has some of the same characters present, but Sebastian IS ALSO present, meaning that Isaac must come before Mozart since Sebastian isn't there yet
9.) Personally, I think Jean goes here. His TDTHCTTM doesn't have anyone else but Comte in it, and there's no mention of anyone else, so it's unclear just when he came to the mansion, other than the fact that there’s no mention of Sebastian which is why he could honestly go anywhere before that. Although, if Mozart came a year before the current events of the story, then that would leave a pretty narrow time frame for both Jean AND Napoleon to join within that year. And with how full of despair Jean is, I feel like he's been here longer than at least a year. Other than that, I'm not really sure where he goes. Comte doesn't mention any other guest when introducing Leo, Dazai, Theo, and Vincent to Arthur, so perhaps at least somewhere after Arthur. Still, I think at least him and Isaac’s placements are interchangeable
10.) For previously stated reasons, Sebastian has to appear after Isaac and before Mozart, but he’s not present in Jean’s TDTHCTTM (and you think the history fanatic would be or at least helping out) so I’m gonna say he goes after Jean
11.) Again, as previously stated, some characters before this are present, and since Sebastian is also there, Mozart must go here. Also it was said in his route (I think when they're taking shelter from the rain but I could be wrong) that he's only been at the mansion for a year, so it makes sense that he'd be one of the last residents
12.) And as stated many times, Napoleon is the last person (before MC) to come to the mansion, so he goes here
