"So...what's the premise for this game?"
You are a survivor of an apocalyptic scenario -- it seems humanity has been wiped out. You are marooned on a desert island, but you are not alone.
You awaken to a strange young girl that is trying to get you up. Your mind is fuzzy, you cannot quite remember what is going on or how you got here. She is hungry, and so are you, you need to find food. You find a fishing pole to fish and catch food, but need a way to cook it, so you need to build a fire. After you build a fire you need to forage up materials to make a tent and bed to keep you dry while you sleep.
From here you will eventually meet Shan(Beauty). Beauty was the assistant of the creator, Shan. Shan was the person that built the island and the AI-Girls. Beauty(Shan) was his assistant. When Shan perished during the cataclysm, Beauty, Shan's first created, assumed the mantle of the creator and maintained the Island and the AI-Girls in his stead. She now wanders the island amused by the idea of becoming a great treasure hunter.
Once you get past this point you are finally in control. You must now develop your relationship with the girls. (Note you can make all the girls custom, you don't have to stick with Tsubomi "A bud," although I do suggest getting her story)
You need to decide how you want to treat the girls, as there is truly no right or wrong path in the game, but every choice effects her future as all interactions are permanently remembered. Do you want to be the gallant knight in shining armor? The typical boyfriend? The sex crazed creeper? Or the abusive narcissist? It is up to you...
Generally, this is your primary play options/objectives:
1. Interact with the girls as often as you can. Find out their likes and dislikes through chat dialogue. You can tell by their demeanor and facial expressions if they like it, feel meh about it, or are offended. All responses add points and exp, just positive responses increase motivation, mood, fatigue, and morality with positive multipliers, some more directly than others, and may add to their traits aside from sociability. Negative responses will create negative multipliers that will leave her upset, exhausted, open to illness, grumpy, etc., as well as potentially increase her darkness and vigilance traits.
2. Always date each girl once per day. Just a brief, follow me, with added things such as eating together (at a table), gathering materials together (increases her instinct which will make her gather more materials, which increases her instinct also - loop), or relaxing and spending time together. Unless she begs, try not to H her during this stage, try to get through all the girls. This will at least make sure they are all fed and will reduce sickness (unless you want them to get sick).
3. Deal with status ailments quickly. Every few minutes you will want to open up your phone and check all the girls status. You will see them get hungry, tired, exhausted, stomach aches, colds, etc. When these status issues strike interact with the girls as fast as you can (fast travel to the nearest location to save time, they freeze in place when you do, reduces chase times). If she is:
Hungry - get her to follow and make her eat with you, (if trust/reliability is high enough) or in dialogue, suggest she eat. You can also give her food in dialogue by "give item" choose the foods tab, then select the prepared food.
Tired - get her to follow you and sleep together on a bed, or in dialogue (if trust/reliability is high enough) send her to bed.
Exhausted/Fatigued - get her to follow you and take a break together (bench/couch/etc), or (if trust/reliability is high enough) send her to take a break in dialogue.
Stomach Aches - make/buy a "gastrointestinal medicine" and bring it to her. Open dialogue and select "give medicine" then the appropriate selection.
Colds - make/buy a "Cold Medicine" and bring it to her. Open dialogue and select "give medicine" then the appropriate selection.
Overheating - get her to drink a cold drink or consume anything that lowers temperature. Get her indoors near a fan (7m seems to be the distance threshold) or take her to a watery or rainy area (out of the island section she is in now) and get her to follow you through the water -- or all of the above.
Temperature low - feed her foods/drinks/items that increase temperature (i.e. Coffee). You can also make sure she stays dry, bring her near a bonfire/fireplace/woodstove, etc. Keep her there until her temperature recovers. This can take more time than any of the others as it seems they need to be within 1-2m of the heat source, also sometimes it doesn't return to normal until after you end the "follow me" routine although it still seems to count, just doesn't show a visual improvement right away. Again, or all of the above.
If she faints from any of these status ailments you will get a pop-up on the bottom right ["Girl's Name" has fainted]. Find her location ASAP and go pick her up and carry her to a bed to lie down. Check back often as you want to tend her issue as soon as dialogue becomes available (worst case she will get up without offering a chance for dialogue). As soon as a dialogue option is available, refer to the above instructions for remedying the situation.
(AFK a few, at work, will return shortly with more interactions and special training - in roughly 30 minutes or so -- forgive any typos or grammatical errors, typed in a rush)