Probably one of my favorite Re dog designs has to be my merchant design!! The amount of times I was ever so grateful to see the merchant next to a checkpoint when I played Re 4 is unimaginable.
For his breed, I chose an Australian Koolie, very little is known about him. He seems to set up shop on the go and carries a wide range of goods. He has an unknown connection to the Duke.
Where after Venus ends up in a coma Koolie comes across a doll, feeling compelled he brings it home. After a few weeks ( a few weeks because he avoids being in the house when not taking care of Venus) he starts noticing that the doll is possessed.
Thinking that Venus os the one controlling the doll he starts obsessively trying to communicate, and take care of it. In reality its not Venus its Y/n (your self insert or oc), they have no way of communicating this to Koolie though.
Seeing this man losing his mind out of grief, Y/n starts trying to help out, and comfort him. Though what they can do is limited due to the fact that the only reason they possessed a doll in the first place is because they are a really weak spirit (maybe weak because they're technically still alive, being in a coma like Venus is).
Them trying so hard to be nice to Koolie is what tips him off to them not being Venus, but Koolie keeps pretending they are because the man wants to stay in denial even if only for a little bit longer. I imagine as Koolie starts to accept that Y/n is not Venus, he either becomes a platonic yandere for them (still being very much in love with Venus, and holding out hope for her to wake up), or a romantic yandere ( coming to accept Venus is never really waking up, and latching onto Y/n instead).
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And if you want to go down one of the angst routes.
Venus wakes up after Koolie moves on (romantically), and Koolie goes right back to her forgetting his ghostly sweetheart, leaving Y/n to their fate as a ghost never to return to their body.
Or Venus wakes up while Koolie is still tricking himself inti thinking Y/n is Venus. Koolie gets really pissed at Y/n for pretending to be Venus (even though they are doing no such thing), and destroys the doll which harms Y/n's soul.
Fir extra angst points you could have it so Venus's soul hung around her body, but she was choosing not to reenter it, or her soul was gone the entire time cause she instantly chose to move on leaving Koolie behind.
I've been struggling to decide between koolies and kelpies but I'm an absolute fool. The obvious solution is to get two that look almost identical so everyone is confused at which dog is which breed. Life is too short.