For me soulmates aren't related to love. It's the person you're so close with you could share your soul with him/her. He/She knows everything without you even needing to say a word, almost telepathy. It's closest to best friends, as there are always things your lover wouldn't know or understand about how and who you are, but your soulmate will know instinctively.
That doesn't mean you love them in a romantic way, cuz they're closer to a part of you rather than another person.
I made the difference watching the KDrama Boys over flowers if you wanna an example of what I mean. I'm happy to see that sort of definition here ^^.
Btw, thanks to the TL for the effort of choosing the right word, it must have been frustrating with all these choices ^^'
It's interesting to see all them though, so I'm grateful for that last panel too.