Raws
Here
Pages 4 and 12 Rio says "ecchi" (えっち)
Page 13 Protag thinks "ero" (エッロ and エロすぎ)
Page 14 protag says "eroi" (エロい) and Rio says ecchi (えっち)
Page 15 protag says "tottemo ecchi" (とってもえっち)
Can't fault the TL, I see no way this can be localized properly in a way that won't seem like weird logic jumping.