I think it is rare for J-Drama to have serialized seasons. One exception recently is Shinhannin Flag. Usually they have SP or even movie. But the movie already made back in 90's. Yes, I know besides SF there are more of J-Drama to have multi-seasons. Then I agree with you this is a Drama worth for long binge.
The Seven Sins and Seven Virtues was elaborated firstly as I recall in Dante Alighieri's Divina Comidia. While your gluttony interpretation not far-fetched, your movie Helter Skelter is closer to Vanity/ Pride. Gluttony is close with Greed/ Avarice.. Avarice is greed toward health while gluttony greed to feed self incessantly. I couldn't remember which movie falls to the Gluttony.
Nanji no Na Episode 5 Eng subs are out over at D-Addicts and Drama Otaku, enjoy! pic.twitter.com/l8tqb2dpvW— GEO9875 (@GEO9875_SUBS) May 7, 2022 here is 5th