I, the Flame-Haired Blazing-Eyed Slayer, Am a Soul Reaper

The protagonist is single. No gender-bender romance.

Aizen: "No one stands in heaven from the very beginning, neither you nor I, not even God. But this unbearable vacancy on the throne of heaven is about to end. From now on, Shana, I want you to stand at the summit with me."

Kuchiki Soshun: "If I weren't the heir to the Kuchiki family, and you, Shana, weren't a commoner from Rukongai, would everything have been different?"

Kisuke Urahara: "The Midnight Lost Child makes time lose its way at midnight. Shana, I think I've lost my way while spending time with you, too."

Shana: "Shut up, shut up, shut up! I thought of you all as good brothers, and you actually..."