Maybe relationship headcanons for Luppi and Nelliel with the reader?
Luppi:
He's self-centered and a bit shallow, so he'd love a significant other who praises him, compliments him, and constantly asserts he's fantastic.
However, this man isn't used to human compliments, so he might act like he knows he's pretty when you tell him, but his heart always skips a beat!
Absolute whore for attention (might die without, seriously, don't push your luck)
Luppi would force you to live with him, tbh. If you're human, prepare to be abducted indefinitely to Hueco Mundo.
Loves pdh (gradatory) he'll def be the one who puts a dog collar on your neck and walks around with you.
However, he's melting in your arms when you're alone. He can't help but enjoy your scent so much, to fall asleep on top of you and fantasize about you staying with him forever.
Luppi's best quality as a partner is he's perceptive of your feelings, even if you try to hide them, while his worst is that he's enough of a cunt to ignore if you're not feeling okay if he's pissed with you.
Nell:
She can be a bit suffocating, but give her time to get used to the fact you're not leaving.
Nelliel, unlike the other Espada, enjoys the life she's got in Hueco Mundo, and she lives enjoying her every day in her way, which she's grateful you understand. "Why," you might be asking. Well, because she wants to share that with you!
Nell takes you to all the cool places she's found in Hueco Mundo, taking tea with Pesche and Dondochakka and fishing in the sand! Escaping danger when you happen to bump into someone looking for a fight.
Nelliel carries herself with such elegant parsimony that watching her fight became one of your favorite activities! More so because it's rare that she agrees to jump into a fight.
Nell's best quality as a partner is that she's considerate, while her worst is that she might be Incomprehensive.