Blood Debt - The Falcon and the Winter Soldier (Bucky x Zemo)
17 parts Complete Three years after The Falcon and the Winter Soldier, an alien computer virus is spreading on Earth. This virus explicitly targets and disrupts Wakandan tech. It's currently being passed around the black market, and Bucky Barnes, the White Wolf, is trying to stop it. He petitions King T'Challa to let him once again solicit the help of Helmut Zemo. His black market knowledge could prove critical to tracking down the source of the virus and safeguard Wakanda.
This assumes Bucky and Zemo kissed during the events of TFATWS, but otherwise everything fits canon. I aim to hold to canon as much as possible, except assuming both men are bisexual and are attracted to one another. There is a plot and investigation. It's also heavy on sexual tension with a bit of non-graphic smut. This from Bucky's perspective.
tl;dr this story is my vision of the Falcon and The Winter Soldier S2, but this time, make it gay.