Well in sexiness, to me it's Ayaka... In H!P concerts she always catches my eye even if I don't really try to pay attention to her or anything. I always see her and think "ah, Ayaka is so sexy"
Her smile and all. I don't know it that counts as being underrated, ROFL! (I'd love to see her do better in our annual hotness poll, but since musumes are turning 18, I don't see her even making it to top 10 next time)
And IN A WAY Koharu is: even if her Kirarin singles have been selling like hotcakes some people just can't give her any credit. The point is that SHE makes a great Kirari, she is adorably dumbly goofy and sparkly. I think she'd deserve to be more popular than she is.
Also, *I feel* that members who were once the aces of Momusu are kinda becoming underrated these days, like Nacchi, Gocchin and Rika. People just seem to forget about all the graduated members and follow the mothership that is Morning Musume. It's to be expected, but still a bit sad to see how the people who made Momusu's existance possible are being pushed into a corner and forgotten about. And I always take it personally if I see someone show disrespect to 1st gen, cuz if it wasn't for those 5 girls you wouldn't have Yossi, Risa, Reina, or any of the girls from the following gens (not to mention the other units!)... So yeah lol. Pleaaase don't underappreciate the 'old members'