I believe what you're feeling is the first stage of syphilis.
On the real though i hate it when older characters always try and maintain an image of being in control all the time even if theyre not very mature or well put together so i like how Seriho has confidence on Sarasa's decisions and is okay with leaning on her since she knows Sarasa is very capable but at the same time has been shown also supporting her when Sarasa is insecure and Seriho remains calmn when it counts, a very good dynamic.
I am surprised she hasn't mentioned their age gap at all though i mean its pretty clear here shes fallen in love and 8 years is quite a bit of years, maybe later? Im okay with it not being a problem theyre a pretty good couple.