Damn, I am a big Haikyo fan and was looking forward to Haikyo content but this is pretty much just sex. At least I can contribute something-
Finger condoms are kind of a thing, they aren't really for stopping STD transmission unless you have open cuts on your fingers - you should just wash your hands before sex if they're dirty. You have no mucosal membranes on your hands so you can basically stick them in anything and wash them and you'll be okay - this is why you can only contract COVID-19 and other viruses by contact contamination if you touch your own face before washing/sterilising them. Finger condoms and gloves are usually used by people who have long-ish nails or french nails, or you can get ones with different textures and stuff.
This might be just a myth, but I've heard there is a 'New York lesbian' thing around some Korean chicken shop that gives their customers finger condoms-like things for free so they can eat chicken with their hands without getting them dirty and it is popular with lesbians who ask for extras.