Nice to see this resume.
Lucky ecchi situations and that one male friend. This really feels like an ecchi romcom series from the Mid Heisei era, which is actually kinda nostalgic, since nowadays I feel like the male lead isn't even allowed to have a single male friend and instead there must be at least 3 girls thirsting for him at the minimum. Like harems became a default necessity for generic romcoms.
A Heisei-style ecchi romcom, but with none of the overused comedic violence and violent tsunderes that were the meta back in the day. Sara's been nothing but pleasant so far and Seiji is neither a timid nerdy loser, nor a perverted sexpest (actually a rarity now I feel, but it's an old male archetype that I hope stays dead).
I'm positively surprised about Sara having an attribute like her being sensitive to lies and not being a gullible airhead; that's good since it makes her seem less like a generic, Girl A trophy gf and instead adds to her character. She's also got a mild(?) sister complex with Kou. Do you have a moment to hear about our lady and savior, Kou Saionji?
Anyway, maybe I forgot but it's unclear to me whether Sara and Kou are twins or half-sisters given that they're also classmates and are basically same age siblings. Maybe I should re-read.
Something's up with page 12, it seems smaller than the others.