1. In this universe, it is Matsumoto rather than Isshin who sneaks off to the human world
Sure, there are other ways we could imagine Matsumoto getting custody of the Kurosaki kids, but why choose something other than the lesbian love story version? So in this universe, it is Matsumoto rather than Isshin who goes to the human world and has a love-at-first-sight meeting with Masaki. Later Matsumoto will give up her powers to save Masaki, and then the two of them will get together. Then Masaki will have their children. Not quite sure how that works, but I’m guessing Aizen is involved.
Aizen: This is perfect.
Aizen: Not only will I see what happens when a Quincy bitten by a super hollow has a kid, but I’ll also get to test my two lesbians having children without a man device!
Gin: ..and why did you make that latter one, again?
Aizen: This mind never stops, Gin.
2. Matsumoto will try to help her children’s grief via silliness.
After Masaki dies, the kids are obviously traumatized, as in canon. And kinda like Isshin, Matsumoto will try to make them feel better by being as silly as possible. Only Matsumoto is less about weird incest jokes and/or attacking children (*cough* Isshin *cough*) and more about ice cream and tickling.
Ichigo: How come my sisters always seem to get the ice cream, and I always seem to get the random tickle attacks?
Matsumoto: Maybe I’m trying to make you stronger, Ichigo.
Matsumoto: Or MAYBE you make the CUTEST faces when you get ticked! Like THIS!
Ichigo: (shrieking with laughter): NOOOOOOO
3. Matsumoto would LOVE back to school shopping.
This is less a plot point, and more just an undeniable fact.
Ichigo: Mom? This shirt is too small. Can you get me the size larger?
Matsumoto: Sure! Here!
Ichigo: I SAID THE SIZE LARGER, NOT THIRTY OTHER SHIRTS
Matsumoto: You’ll thank me later!
Yuzu: Back-to-school shopping is so fun!
Karin: Yeah, for real.
4. Yuzu would still do all the housework.
Sadly, this would not change much from canon. Matsumoto likes to leave work for others, much like Isshin. So Yuzu would still find herself doing all of the housework.
Karin: Ever since Mama died, Yuzu started taking care of the whole house for us.
Karin: Mostly because Mom really really loves to nap.
Karin: …it’s a mostly functional household.
5. The kids would know about soul reapers
Isshin decided not to tell his kids the truth about his past, for reasons that remain kinda unclear to me. And it is true that Matsumoto also knows how to keep secrets. But on the other hand, Matsumoto knows how it feels when someone you love refuses to be open with you (*cough* Gin *cough*). And when she saw child Hitsugaya suffering because of his shinigami powers, she told him the truth about it. So I think Matsumoto would be open with her kids as well.
Ichigo: Wow. So that’s why I can see ghosts?
Matsumoto: Yeah. That’s why.
Ichigo: Man, I can’t even imagine having to grow up without understanding that!
Matsumoto: It would be pretty rough!
5. Matsumoto and Rukia would bond
When Rukia showed up, she wouldn’t have to hide her identity as a soul reaper. Instead, she and Matsumoto could talk about everything.
Matsumoto: Listen, it’s okay to feel bad about your brother. It’s okay to feel guilty.
Matsumoto: But you’re doing good, you know? You feel like you can never live up to his expectations, but you’re still trying. You care about your duties and you care about your friends.
Matsumoto: It’s okay to feel bad sometimes.
Rukia: T-thank you.
Rukia: Ichigo is lucky to have you as his mom.
Matsumoto: I keep telling him that!
6. Ichigo’s interactions with Gin would have an extra layer.
Because Gin would know, remember, that Matsumoto is Ichigo’s mom.
Gin: I’m afraid I can’t let you get past, ryoka.
Gin: Also, how is your mom doing? Will you tell her hi from me if you don’t die?
Gin: I’m just teasing you!
Gin: But seriously tell her hi from me.
7. In Soul Society, Isshin and Hitsugaya would be together in Squad 10.
Since in this universe Isshin never left Soul Society, Isshin would still be the captain of Squad 10, and Hitsugaya would be his lieutenant. They’d still investigate Aizen’s “death,” of course. And Hitsugaya would still have his bankai.
Hitsugaya: I don’t trust Ichimaru Gin.
Hitsugaya: I think we should investigate him, Captain.
Isshin: You’re so cute when you’re an overachiever, Toshiro!
8. Ichigo would have dust-based powers.
In canon, Ichigo’s powers turned out to be kinda the same as his dad’s. So in this reality, Ichigo’s zanpakuto powers would be loosely based on Matsumoto’s. And that means killer dust.
Ichigo: So you have killer flower petals, huh?
Ichigo: That’s interesting. My power is kinda similar.
Ichigo: Actually, really similar! We’re like power twins!
Byakuya: OKAY NOW YOU ARE TRYING TO MAKE ME MAD
9. When the advance squad came to Karakura Town, Hitsugaya and Matsumoto would reunite.
I choose to believe that even in this universe, Hitsugaya and his advance squad would still come to Karakura Town after the first Soul Society arc. In canon, Hitsugaya somehow managed to never run into his old captain Issin. But if Matsumoto were there instead, I’m sure she’d make sure to catch up with her old subordinate.
Matsumoto: Toshiro!! Look at you!! Just as adorable as I remember!!
Hitsugaya: PUT ME DOWN I’M A LIEUTENANT NOW
10. Matsumoto would face off with Gin in fake Karakura Town.
Like Isshin, Matsumoto would end up getting her powers back and would go to fake Karakura Town near the end of the battle. Only instead of getting knocked out by fighting against Aizen, I think Matsumoto would choose to confront Gin.
Matsumoto: I can’t BELIEVE you told my son that he should just go home because he can’t beat Aizen, Gin!
Matsumoto: Look at him! He’s got anxiety now!
Gin: Anxiety? Why, I was just giving him a nice motivational speech!
Matsumoto: YEAH WELL YOUR MOTIVATIONAL SPEECHES BREAK PEOPLE EMOTIONALLY