Junkrat

He's more curious about you being asexual than you being worried, tbh

Will probably have a few questions for you about asexuality and what that would mean for your and his relationship while you're talking about it

After he gets a decent understanding on the situation, he's not bothered by it at all

He's actually surprised you would think so, but he doesn't say that aloud in case it would hurt your feelings

Instead he goes off on a somewhat overenthusiastic (but when isn't he) rant about how he's perfectly happy with you, sexuality aside, and that he's 110% supportive of you

Probably asks if there's anything he's done that has made you uncomfortable in the past so he can learn not to do it

Also asks what your extents of other physical affections aside from sex are, just to make sure you're totally comfortable (whether or not you're okay with kissing and if so if there's places you'd prefer to not be kissed, etc)

He may slip up on occasion but overall he's doing his best and he's totally chill about the entire thing

Sombra

She's indifferent about you being asexual, really

She's not a super actively sexual person herself (work and life and being busy in general gets in the way)

She's upset that you'd think she'd leave you, though, and she tells you so

Immediately patches it up by telling you that as long as you're comfortable and happy, she'll be the same

Asks you about your limits in general to make sure she doesn't overstep

Then goes back to reassuring you that you're amazing and perfect and that there's nothing that would get in the way of her relationship with you, especially something such as your sexuality

She's just gonna keep complimenting and assuring you until you blush, tbh

Hanzo Shimada

He's completely respectful and understanding, both about your sexuality and your worries

Ever the gentleman

Simply and gently assures you that there's nothing that could change his opinion of you

He only wishes you had told him sooner so he could take it into account, but he also understands your hesitation

Probably wants to hold you close and just kinda snuggle and chat to lift your spirits afterwards, as long as you're comfortable with it