
Actually, no. Japanese Buddhism is surprisingly open to partaking in sexual pleasures. Monks were known to have relationships with geishas and prostitutes back in the day. Also (and don't quote me on this, it's been a while lmao) Japanese Buddhism is what ushered in the 'culture of homo and bisexuality' as they were quite open to it during the Meiji era. Although, iirc, the relationships were almost always pederastic in nature (adult man/monk & adolescent boy).
Again, it's been years since I studied this so better to look it up if you're really interested.

Right, so whilst the major religions in Japan are Buddhism and Shinto, a lot of people aren't actually devout and practice it in their day to day life (at least from my experience and what I've seen). Most do follow certain rituals which are based off religion such as shrine visits, ceremonies for birth, funeral, weddings, etc. But it's more of something that's tradition and less about the religion itself (am I making sense? Lmao)
With regards to the MC or general population, not knowing about these monks who can marry/drink alcohol/eat meat, it's honestly not surprising. I think generally, most people when they hear Buddhism/monks think of ascetic Buddhists-- those who practice self-discipline/abstaining from pleasure to achieve enlightenment.
There are also lots of Buddhist schools being practiced in Japan (Zen, Shingo, Nichiren to name a few); as such, different schools have different allowances in their practices. Not sure if the manga's mentioned which it's portraying, but it's definitely one that allows marriage (example of one is Pure Land Buddhism) Honestly, it's a quite normal life apart from the robes and prayers, etc from what I recall. Some schools even allow marriage to foreigners (times truly are changing haha)!
I will say though, being a smut manga and all, it does exaggerate the whole sex thing imo... monks would still practice self control and not have sex every chapter smh #-.-)
Also again, disclaimer since this is just all from the top of my head. I'm not a Buddhist or some scholar, so some info may be a bit too generalist. It was something I had to study a few years back oTL
Like...offensive?? As expected of Japan, sexualizing monks too. Migoto