^ We don't know if they are all into girls, the oldest one particularly but there are no evidence for youngest one too
The oldest one seems straight to me, I think she's aware of her friend's feelings but doesnt reciprocate. She's also focused on getting a husband
The youngest has a romantic two girl friendship with Sakurai at best, we don't really know if it moves past friendship
Anyhow, this series is simply lovely to read, very well written, the concept of all four sisters in the same age period.
It's unfortunate that the yuri levels are kinda low, but it was sweet nonetheless, truly a personal favourite!