Pretty much impossible you find a monogamous game with a virgin MC. Not likely, thats too close to real life.
Devs create games that are fantasy, not real life. Thats why so many games are harems.
You should give Sexnote anotehr chance. It gets very good since MC has a nice relationship buildup with his sister and girlfriend. MC's girlfreind is also inexperienced like him, she als goes to therapy with him to gain confidence. Its a sweet romance. Honestly the MC has the most natural relationship build up with his girlfriend, sister and mom.
Bound by Lust is one of my favourite games <3
I highlt recommend it.
I have to warn you tho. The start of the game (first 10 mins of the game) are from the POV from the greatest Guardian in the past. MC is his descendant.
You will probably like the interactions between the MC and some of the girls (since you are looking for an inexperienced MC).
Dana the school slut is the daughter of the CEO of the biggest company of the city (its hinted her parents are from the mafia too). She plays the MC on her little finger. Many actually hate her due to her attitude at the start.
She actually likes the MC and finds him special, but she is not aware of this herself (since she is a slut and love/feelings is not something she is familiar with).
Another good female character is Suzie. She is friends with Dana but has more respect and dignity. She turns down all playboys and rich kids. She sees the potential (husband material) in the MC after some time.
She is kinda of a tsundere, since she does not make things offcial with the MC, but also kinda dates him.... i hope that makes sense to you

you will understand after playing the game.
(My advice is to be confident with her. Alsways be bold and select the choices that will go for her. She likes that, but never openly says it)
There are other character that take advantege of the inexperience of the MC. So I think you will overall enjoy this.
Another recommendation is :
Unlimited Pleasure by Waifstone
MC is a virgin with no experience with women. It can get awkward tho lol
I think this will fit most of the criterial you are looking for.
MC is very awkward with women at the start.
There is a Dynamic Dating Simulator in the game.
Meaning if you select cringy and stupid stuff to say and do during dates, the women will not like it.
You have to know what the girls want and like. You have to know more about them, similar to real life.
All love interest are MILFs. So be warned.
I personally like htis baout the game. All of them ae virgin-like MILFs
(Well Bianca is a ex-porn star lol)
I highly recommend this. This is the closes thing you are looking for. An awkward virgin with no experience. Who is surounded by MILFs with different kinds of experience.
- A mommy dom Teacher
- An ex Porn Star
- A thug Mom (a thug in her younger years, turns sweet and caring mother)
- A female best friend MILF (she was fat and likes to eat a lot, but you kept friendship with her)
- A care taker MILF (She was like a nanny for the MC)
- Two sluts tunred nuns (wild whores in high school turned sluttly nuns)
- A stict Grannny principal
- A MILF action movie start
- A MILF life guard on the beach
Its a slow burn game. All the women have more experience than the MC. Some are kind and understanding. Some are direct with him. But all have a good romance buildup. Its all very sweet.