The description made it sound like your typical shoujo story and the mention of getting a guy friend to help her choose lingerie made me wonder whether it was going to be smutty to boot, but I was pleasantly surprised to find a really cute and breezy story!
For starters, the premise isn't actually as ridiculous as it originally sounds. Yuzu's a tomboy who's always been referred to as "more manly than guys," so she avoided asking other girl friends for advice about her underwear for the school trip out of embarrassment. It just so happens that her very close guy friend, Ken, is someone with whom she can talk about anything, and his house is... a lingerie shop. HA! It's a rather interesting twist, actually, and more than effective for a story that was originally supposed to be a oneshot anyway. It's also quite nicely paced, so there's a good balance between character development and story progression.
I really adored Yuzu, who reminds me a little of your "every girl." How many girls can say they've never gone through at least a period when they were like Yuzu, thinking about comfort first and suddenly finding themselves stranded when they have to dress to impress? She describes herself as "not honest," but frankly on the scale of shoujo heroines, I find her remarkably gutsy about her feelings, choosing to tackle misunderstandings head-on rather than mope. Her friend Ken is the same, so it makes for very nice reading when the two leads are so sensible. They make an adorable couple, and it must be dang handy to have a bf that can pick out your wardrobe!
The art is really nice - sharp, clean lines, lovely shading and so on. Yuzu looks rather cute despite the straight fringe, and Ken is... well, a bishie. Nothing at all to complain about in this department.
Give this a try; you won't regret it!