Bonus question: How can I get into the route for Arnette's sexual scene? ;)
I'm not sure which you're referring to. (Although there's no full sex scene yet with Arnette.) There's a brief shot of him giving a blow*** to MC(imagination) after lunch. Then there's the scene with him in your bed(imagined) after you choose to hangout with him and be brave enough to tell him how you feel. Both of these unlocks are guaranteed if you choose to fantasize about him in the photo scene. If you don't fantasize about him, there's still a way to get the other unlocks, make sure you at least choose to
- Reciprocate with a confident stare. (photo scene)
- Glance at him again. (photo scene)
(If you reach this point and not fantasize, you get a small scene where Mike and the other officer will gossip about him.) Make sure you choose: "You shouldn't take advantage of his eagerness" and NOT "Better not interfere".
Make sure to also stay in line during the inspection.
(By the way, as I said in the previous comment, I'll be making a small in-game guide that will give hints to what each choice does.)