That looks like it will get confusing and cluttersome real fast as the game gets bigger and bigger. Like a family tree with an extensive family lineage, but one that shoots out in all directions.
The gallery idea has merit. A lot of H-games have a gallery and hint system that work through character profile pages. A couple good examples are Mall Creeps and That New Teacher. Mall Creeps has a very organised image gallery with the images locked and all black silhouettes. You hover over the image and it gives a clue as to how to unlock that scene, acting as a guide system without ruining the fun of figuring out the specifics yourself. That New Teacher does similar, but instead of through the gallery, it has the guide system as a To Do list where you can simply read what the next step is to progress that particular scene, with each scene having a name, and each listed title revolving around a character so you know what to do to see that character's particular scene. To give an example, if this game used that latter system, it would have several things like, perhaps, "A Night at the Club" and then under it a description like "Mom wants to go to the club on Saturday. I wonder what would happen if she didn't have the money though". Then, when you refuse her money it would change from the 'I wonder what' part to something like '"I should follow her tonight." Meanwhile, the sister would say "I should talk to her when I get back from the club with mom. (Progress Mom's story 'A Night at the Club' first)."
A couple honorable mentions for good hint-like guides are Cozy Cafe and Lustful Sin. Lustful Sin has profile pages that act as a guide to the next step for that character, which you wouldn't be able to copy due to having a much less linear gameplay in your game, but the way the gallery has the hints on it is a good layout you may be able to draw ideas from. I suggest checking some other devs' works and see what suits your style best. I'm not saying copy their ways directly, but maybe grab some inspiration from it. You definitely want the system to be a clean and tidy affair, not a jumble of words or images.
By the way, great work thus far. I'm enjoying each new update.