It is, but you need to choose Natsumi only route and not the harem route on chapter 5. Although, Chapter 5 itself is still in development. There's no ff girl on girl in chapter 1-4.
Is Natsumi really MC's sis? Or childhood friend coz I'm very into incest but I don't like to change the orginal story(childhoodfrndxMC) to incest just for fun so what is she to MC in story cuz I know patreon won't allow incest, did you change her into childhood friend becoz of that or is she really meant to be the childhood friend
And sorry for asking wierd questions like this xD