When Twilight Sparkle discovers a long-standing mysterious meeting among her five closest friends, she just has to get to the bottom of it. Despite her fears, her investigation leads her to some friendship lessons she never expected.

Spoilers list specific tags by chapter, in case you'd rather not be surprised.

Night 1: Red-Hooved - Cadance/Shining, voyeur Twilight (characters younger but not foals)
Night 2: Seeing Double - Rainbow/Cloudchaser/Flitter threesome (no direct incest)
Night 2: Fifth Date, First Time - Rarity/Thunderlane, romantic, defloration
Night 2: A Canterlot Night - Orgy, Pinkie/various mares and stallions, double penetration, voyeuristic bondage, lots of other voyeurism, touch of romance
Interlude 1: Paradigm Shift - (yes, not an interlude from clop) Twilight/Applejack, romance
Night 3: Animal Husbandry - Fluttershy/tentacle creature, egg implantation (everything consensual)
Night 3: Tradesies Pinkie/Morning Mist, Twilight/Applejack, futa, creampie, massive ejaculation, Rarity, Dash, Fluttershy solo, voyeurism, exhibitionism
Interlude: Second First Time Twilight/Applejack, futa, creampie, outdoor sex, massive ejaculation, moderate impregnation fetishization
Night 4: Three For the Road: Twilight/Applejack/Pinkie/Misty, futa, group, triple penetration, creampie, massive ejaculation
Night 4 Post-Game: Sleep Over, Part 1: various main six truth or dare shenanigans up to and including oral, CMC voyeurism. CMCless version for those who object to foals in clopfics will be done when part 2 is finished
Night 4 Post-Game: Sleep Over, Part 2: As previous chapter, plus CMC threesome, Twilight/Rainbow/Applejack romance
Interlude 3: Trios: defloration, Futaloo + Sweetie Belle, Spike + Apple Bloom hemipenis double penetration
Night 5: Window Shopping Rarity/Thunderlane, Fluttershy Voyeurism, Exhibitionism, Masturbation, Creampie. CMC half: Futaloo/Sweetie Belle/Futabloom/Diamond Tiara/Silver Spoon, Defloration, Creampies, light submission.
Night 5: Plus One Rainbow/Twilight/Applejack group sex, heavy teasing, sappiness. CMC half: Futabloom/Diamond Tiara, power play, class roleplay, domination/submission (consensual), awkward adolescent feelings, creampie.
Interlude 4: Spectators Futadash/Futalight/Applejack, Rarity/Thunderlane, Voyeurism, Creampie, Futalight/Futadash/Futajack/Rarity Triple Penetration, All the semen everywhere, cum inflation
Interlude 4: Invitations Apple Bloom/Diamond Futara, pretty much just sweet sex, also lots of story first