I read this manga years ago so I don't remember much but I would appreciate any help I can get. So the manga was a collection of one shots I think and the one I am trying to remember it was about a girl who considered herself not that beautiful and/or outgoing compared to either her sister or her twin, anyways her sister/twin has a date and couldn't make it so she asks the sister to go in her place and so the sister dressed nice (and wore a blonde wig I think) she goes on the date and really likes the guy but when she goes back home she gets sad thinking the guy doesn't really love her but instead loves her twin/sister and I think refuses to go on another date. After this my memory is pretty foggy but I think the guy may have already known it wasn't her sister or else he fell in love with the girl so when he saw the twin/sister he knew it wasn't the girl he loved. And in the end the guy and girl get together. Sorry, I don't know if all my information is correct and I know that sort of plot is found in other manga but if anyone know or thinks they may know of something similar please tell me!

Shoo, Nothing to see here!

Reading your summary is giving me flashbacks of a shoujo I read years ago with the same premise as the MC going to a date with her elder sister's friends and ends up liking this boy who is actually dating/wanting to date his sister?? And she gets wet in a fountain and trips with heels she's not used to wearing and makes a mess out of her self. A typical shoujo if you ask me but I don't remember anything else. Maybe it the one?
Sorry, I'll let you know if I remember the name.

Your description is making me remember more of the one I'm thinking of, I think it could be the same one..
ugh just wish I knew the name ;-; I keep thinking of the manga from time to time but I can never remember the name or any key details that would help me find it and it's really starting to bug me. I tried to look under the tag "talking the place of a sibling" but had no luck QAQ thx for replying at least, hopefully one of us can remember...

Shoo, Nothing to see here!

Shitsuren Biyoushitsu, maybe?
To be specific: 3rd story - Kono Koi wo Mousukoshi Dake
This is the closest to your description, but there are some details that differ, such as the wig. In this story, the sister who goes on a date dresses nice and trims her hair.

If it's not, there are another two short stories I remember with a similar plot:

Tsumi Koi - 2nd story: Until I Fall in Love

Ten Kara no Okurimono - 2nd story: Reflect Me in Your Eyes

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I think it was possibly a Josei, I remember the art being a bit more mature looking (if that makes sense) and I'm pretty sure she ended up with the same ML she liked, thanks for replying though, I read all the ones you said and they were pretty good, it seems I tend to like stories where the MC disguises themselves as someone else XD

Shoo, Nothing to see here!