Momioka Risa

Risa is one of Rito's and Lala's classmates.The mischievous, cheerful best friends of Haruna, Risa spend as much times as she can with Haruna, Mio and Lala.

Personality
One of her favourite occupations is to grope other girls' breasts and whisper naughty things into their ears.This may imply that she seems to have tendencies towards lesbian, but in manga chapter 147 she, although only in jest, attempted to seduce or rape Rito, which makes it debatable if she actually could be bisexual.

Whenever Lala inquires about Earth culture and habits, the two divulge as much information as they can for her (although it is often misleading and perverted). Risa and her frinde Mio are known for their playful habit of groping other girls.

Rito Yuuki
It has been shown that Risa might have feelings (or at least lusts) for Rito, but it hasn't been detailed if she was serious or joking.