I didn't find it to be all that long. It's not actually that grindy per-say either, but lacks anything in the middle. That empty middle makes it FEEL like more of a grind than it is. You should consider adding more events in the middle to build up to sex, like when you first reach the relationship requirements for touching, a more detailed and repeatable groping scene. A blowjob before getting to sex too. Something to flesh out the middle would likely do a lot to help with the feeling of it being grindy.
The video's are okay, but I would also strongly recommend writing more detailed scenes. HTML games are largely narrative and benefit immensely from the writing. I am somewhat biased there but, to be fair, I get nothing out of pictures or videos. They don't turn me on or get me off at all, and most people here can find things longer and to their taste just about anywhere anyways. So lean into writing the scenes out more instead.
I would also suggest having it check for terms like sister, cousin, or niece, for incest themes, girlfriend for ntr themes, and have parts of the scene you write swap out if these terms are detected. That will let players tailor their experience a bit as you clearly intend with the level of flexibility offered in the intro picking everyones names and relationships.
Finally, it's an early release, but more repeatable scenes would be good too, without needing to buy things to repeat those scenes. I.E. When I walk in on them in the bath or shower, I fully intend and want to fuck them in said shower.
On a bug note: I seem to get interrupted MORE often when his suspicion is lower than 20%? I got it down to 13 and was interrupted almost every time. This should probably be adjusted some, and I would suggest changing it to a SINGLE check to determine if you're interrupted, per scene. Otherwise it can be extremely irritating for players as it became for me. While the one-line scenes was ultimately what made me stop playing for now, till there's more content, the constant interruptions when I did reach a scene had me about to quit anyways.