Here are the things to do in order to obtain the True End :
1. Hot Spring Event 1
After you recruit Felicia in 2-1, head south and then east from the first save point. Search at the edge of the land for the "Gasping Fish Beneat the Ice" event.
2. Marie's Alchemy Event 1
From the 2nd Save Point in 3-1, head east into the forest there and search for the "Comedic Tragedy of 'F'". It's sometimes possible to get Shurelia to join you before watching this event, so if you have her but haven't seen this one, better get to it.
3. Ayatane's Betrayal Event 1
From the 2nd Save Point in 3-1, go past the forest to the south and search between the two towns down here for the "Scarlet Noella" event.
4. Defeat Lazarus
In 3-1, when you get to the "Twin Canumares" event you'll fight Lazarus. You MUST defeat him before 5 turns are up, or the battle will end prematurely. You MUST reduce him to 0 HP (or OK, or whatever, but actually destroy him -- This is recommended for all of his battles, actually).
5. Demitri and Lilith's Event 1
In 2-2, when you trigger the "Tragedy Beneath the Moon" event you'll fight both Demitri and Lilith. Defeat Lilith and only her. In fact, you might want to even avoid Demitri completely.
6. Hot Spring Event 2
After you first reach 2-2, head back down to 2-1 to the Spies' Quickness save point. Go around the mountain west of you, and search just outside that forest on the other side for the "Ancient Volcanic Water" event.
7. Ayatane's Betrayal Event 2
In 2-2, after the "Ancient Volcanic Water" event, head east and down to those little islands from the tower you came in. In the last one, search for the "Neverending Fantasy" event. This must be done before the 1st Augustine battle.
8. Marie's Alchemy Event 2
In 2-2, after you go up to the forest in the middle of the area and then down the left path, search southwest in this particular region to find the "Thorough Purging" event.
Intermission: You'll fight your first battle against Augustine here. Most say you can beat him (and pretty sure you can, anyway). But if you are really paranoic, you can just play it safe and only kill his minions.
9. Troy's Memories Event 1 (Or rather, battle)
In 1-2, when you trigger the "Emma Loage Forest" event, you'll fight both Troy and Anesha. Defeat only Anesha and the battle will end, and that's what you want. (It is suggested you only kill Anesha in any future battles, regardless.)
10. Marie's Alchemy Event 3
In 1-2, after the battle with Troy, head to the northwest edge, right next to the snow mountains (literally, on the edge of the world) and search for the "Dale Wenso" event.
11. Demitri and Lilith's Event 2
After the battle with Troy in 1-2, head down to the Ferryman's Hideout in 2-1. Head south and inch and search at the top of the forest for the "Forest of the Ice Butterfly" event.
12. Ayatane's Betrayal Event 3
In 1-3, there's this sort of island on the northeast side of the map. Search in the middle of it for the "Gi LaMensa" event.
13. Hot Spring Event 3
After you reach 2-3, find a Save Point and then move down to the Manor at Len Mountains in 1-1. Stick to the mountain as you head south, searching along the way to find the "Niu Spa" event. If you can't find it, you can go and fight with Reicher firs then try again.
14. Marie's Alchemy Event 4
After the battle with Reicher (not a requirement, just using it as a landmark), head north past the disappearing tablet. Then search an inch south of the forest-surrounded mountain to find the "Disappointed Inquiry" event.
Intermission: You'll fight your 2nd Troy/Anesha battle here. I still say to play it safe and just kill Anesha.
15. Marie's Alchemy Event 5
After the 2nd battle with Troy (again, using it as a landmark), head southwest. See that little town that is almost surrounded by forest? Search an inch southwest of it for the "Sheritun de Mollet Guinea" event.
16. Avoid Augustine
When you trigger the "Tegnieri's Cage" event, you'll fight Lazarus, after which he will join you. Immediately, you'll fight Augustine. For this round, DO NOT touch him. Just defeat his minions.
17. Marie's Alchemy Event 6 (COMPLETE)
In 3-3, after you witness both events near the first save point, head by Bel Canto's exit and search in the forest there for the "Overwhelming Enea's Square" event. York and Marie will have to fight a lot of bees here too.
18. Ayatane's Betrayal Event 4
In 3-3, after the lower right tablet disappears, search by the north side of the town clusters in the middle of the area for the "Nikran Fire Spot" event.
19. Hot Spring Event 4
As soon as you enter Fett Road in 3-3, exit and go to Nefteg's Tower. Head to forest east of it and search for the event, "Rofia Spring".
20. Demitri and Lilith's Event 3
Once you get to 4-1, either go back through the tower or do this RIGHT AFTER you fight Jedah. Head down to Traveler's Distance in 2-3. And search at the edge of the forest west of you for the "Wailing Evergreen" event. After you see that one, jump down to Hideout of the Moon in 2-2, and search southwest of the tower that leads to 2-3 for the "Eclipse of the Empress" event.
21. Demitri and Lilith's Event 4 (COMPLETE)
After you battle them in 4-1, they'll join you.
22. Mikoto and the Siblings
As soon as you step into 4-2, head east and hug the edge of the world as you go north. Search at the end for the "Jill Elino Flash" event.
23. Troy's Message
In 4-2, after the first story event (with Judas, Jedah, the siblings, Ayatane and Miko), head to the top left of the area, moving behind some buildings and out of sight. Search up here for the "Rend Boundary" event.
24. Noin Split
In 4-2, after the previous event, keep going past the tablet. When you start going east and south, at the end there's a circle with a square "cutout" in it. Search by what would be 12 o'clock on that circle for this event. The next event you need to see is on a circular trigger, so you can't miss it.
25. Ayatane's Betrayal 5 (COMPLETE)
When you are on the jailbreak scenario, using Ayatane, Troy and Miko, you must not let either Troy or Ayatane to die, at all. Reviving them doesn't count, if they ever touch the ground, reload. This seems to only matter against the Judas/Jedah fight, but play it safe and do this for all battles.
NOTE: By this point, you can check if you are on the right path. After the jailbreak is over (and you are back with York), go to a save point, check the database and look at the titles. If titles 31~50 and 72~80 are showing, you are on the true end, congratulations. If they aren't showing up, you did something wrong. Better luck next time.
26. Ayatane's Health
In 4-3, search west of the tower leading to 5-1 to find the "Forsaken Echt" event. This will only happen if you are on the true end, and will prevent Ayatane from dying later on.
27. Triplets Rejoined
If you are on the true route, when you enter the tower that leads to Ida (5-1), Vivi should join you.
28. Hot Springs Event 5
As soon as you enter the tower leading to 5-1 (and Vivi joins you, if), head back out. Go behind the tower and wiggle your way up to the next platform, search the northeast corner for the "Respell Bath" event.
29. Hot Springs Event 6 (COMPLETE)
After you load your true end data, search where you are to get Raizen and Lazarus back. Then head east, but go north before you cross a bridge over the lava. Search up here for the "Spring of Overflowing Sea". And that's it.