Oh dear, it's not even close to a sandbox game, unless by 'sandbox' you mean a perpetual construction site of an unfinished game which allows the player to free-roam the existing content in a more or less (dis)ordered manner.
A proper sandbox game allows you to make up your own rules and do whatever it is that you want to do without violating the game's own laws of physics. You obviously played Minecraft, so you should know the difference.
Here, my friend, you have a calendar, your own role of a student and orphanage resident and as such, stuff to do, calendar-triggered events, quests of sorts, etc. You have a fixed map with immovable objects and you cannot add or raze anything from it. You can only manipulate your environment to a very limited degree, basically dress as you like, except school, do some gardening and expand the farm. Oh yeah, you can also decorate your room, which is pointless anyway, but whatever, more sand freedom of choice, right? You can only visually admire your PCs attire, hairstyle and transformation and playing paperdoll is the only truly sandboxy feature of the game.
There are other characters in this game who mind their own businesses and appear in this or that location at specific times. There is a limited amount of interaction options, no sandboxy freedom of expression there. You can't discuss Briar with Doreen, you can't set up a foursome with Robin, Kylar and Whitney. Robin is the only person you can go to a cinema with, a cinema which doesn't even have it's own location, so you could go there by yourself, as a proper sandbox game would allow you to do. You can get spanked by Leighton after school, you can do a photoshoot with Leighton during school, you can get fucked by Leighton in the Brothel on Fridays or Saturdays or in his office during school if you've convinced them you're a proud slut, but that's it! A sandbox game should allow you to bring red roses to Leighton and confess your love to them and promise you'll be their bad bad pupil until Day XXX, if that's what you want. Or give 10,000 quid to Landry to sort Leighton out. Nope, you have to follow the script, don't you? And what is a script if not a written instruction on how a story should be played out? Roses can only be sold, end of story.
That's what this game is: a collection of lewd snippets borrowed from other games and loosely connected by an overarching isekai JK-girl leitmotif.
