You know, this is actually a really interesting story about boundaries and expectations. The sister went ahead and made it creepy, but Ayano is just a young girl with no adult figures in her life.
I'm trying to read ahead as much as I can.
The most recent chapter finally revealed what happened between Fumi and that Lighter Woman.
I like this series, I think this is going more in the direction of After the Rain that just a age gap romance, and that's why there are moments that are hard for me to understand. No only Fumi's sister thinking about Fumi and Ayano getting together in the future when she should be having opposite thoughts. Maybe she knows that his brother is "trustworthy", but still would be better to keep an eye on him to ensure that he does NOT put his hand on Ayano.
Other moment is with Ayano's school friend.
In a previous chapter she got alarmed and warned Ayano very clearly to NOT trust Fumi, no matter what, never fully "trust" him because one day he can put his hands on her and there'll be nothing she can do to resist. But then in another chapter she sees ONE romantic scene in a drama ONCE and reverts her behavior completely, trying to convince that Fumi loves her Ayano and shipping the two? It's bizarre.