I've played for 250 days trying to unlock golden shot for the supposedly "true ending" to no avail, so just going to share what I've learned.
There's 4 bad endings afaik:
1. Sister Explosion. Make sister angry while her mood is explosive. Getting caught peeping or filling bad bar during sex works.
2. Return Home. Getting sister trust too low will make father return home to deal with brother mistreating daughter.
3. Unwanted Pregnancy. Get sister pregnant while trust is low/don't have enough money at hand to afford a baby.
4. Sister death. If player ignores sister while not feeling well and doesn't look after, will change condition from sitting in bed to laying down in bed, and if continues ignoring will eventually trigger scene where sister coughs blood and dies.
There's supposedly four good endings.
1. Panty hunter. Get all panties, and brother will show off colection in bathtub immersed in sister panties. Game can be continued normally after ending plays out.
2. Pregnancy. Knock up sister with high trust and enough money. Pregnancy will be acknowledged by everyone, and brother becomes worker to support sister. Game cannot be continued.
3. Leaving Village. If big adventure is completed, then sister mana illness gets healed in exchange for brother fertility, and they go on an adventure alongside Kana. This ending doesn't seem to take into account the two other girls, no matter their favor. Game can be continued normally after ending plays out and credits roll down.
4. True Ending(?). Supposedly it's possible to complete the huge adventure after playing for 101+ days and get the unicorn at the end to give the brother the Golden Shot skill, curing his infertility and allowing to make sister pregnant with a different ending from the seconds one, but so far I've been unable to accomplish this one.
I've attempted a run keeping the little sister completely away from any erotic subjects, so no buying dirty magazines, no sex toys, keeping watch on the panties option status on the bottom right to make sure she's not masturbating, and not interacting with the sex game even once, but that has failed and the unicorn became horny for her anyways.
I'm sharing the save file with the huge adventure at 199/200 in case anyone wants to test out different outcomes based on sister mood, trust, interest and lust, or whatever might work.
I've used the cheat mod to get this far without much stress, so there might be corrupted values and whatnot preventing a proper clear as well.
View attachment 1654881
If this is even a thing, the brother might also be required to keep his chastity intact and not ejaculate even once during the 101 day playthrough, which might have something to do with onii-chan types, otherwise the trigger for the golden shot skill is something completely different.
The only other possibility might be related to an event that happens after day 101+(at least for me playing on Hard mode), where the sister receives some strange seeds from father and plants them, taking multiple events(seemingly random chance like evening encounters) for the vegetables to grow completely, and eventually escape as it turns out they are carrot monsters.
From memory events go by as:
1. Sister receives strange seeds from father and plants them.
2. Seeds grow slowly with weird leaves.
3. Farm gets attacked and sister puts fence around crops.
4. Crops growing slowly.
5. Sister sad because crops dissappeared, saw a monster bringing them into the forest.
6. Guild notified of monster in forest close to village, and brother party sent to investigate, finding monster carrots/vegetables. Party leaves monsters alone, and brother hides secret from sister.
7. More?
Step 6 was around day 230, and by day 250 I got tired of going after an invisible goal and gave up. I might try to get to day 300 later, but honestly I'd prefer to get some confirmation from translated text that proves there more to that.
As for what some people have been asking:
==Kasumi Route==
1. Go to the city and bump into her.
2. Go to the bookstore and bump into her.
3. After creating a new dish for the guild with the help of sister, Kana will mention rhe guild is lacking members, and suggests a genius, with brother learning that Kasumi goes to same school as sister.
4. Brother questions sister at home about Kasumi after dinner, to which sister replies she's very shy and doesn't talk much.
5. Random evening event where Kasumi is attacked by a thug in a back alley and brother saves her, inviting her to the guild, but is turned down by Kasumi.
6. On weekend when sister mentions there's a bookstore event, go to the bookstore and bump into Kasumi, learning her secret.
7. Kasumi will visit the guild later on to apply for the guild, as brother shares her secret and didn't judge her.
As a final note, I sitll have no idea about what the empty second skill slot for the brother is. Might have something to do with the monster carrots or the unicorn.
The prejaculation skill is forcefully enabled in place of iron will, and requires visiting the clinic with the "go out" option during the weekend. The doctor will cure the brother's premature ejaculation with magic or something.
The storyline events like Yukari calling the mayor, the GvG battles and the training camp week always happen on the same days, so it might be nice to note them down in your guide.