Though you may not have known its name at the time, the LOST LIBRARY is a place you've visited before. After defeating SWEETHEART OMORI winds up dropping into a deep hole beneath the stage in SPROUT MOLE VILLAGE, and the book-filled area within served a crossing point between HEADSPACE and FARAWAY TOWN. This is the LOST LIBRARY, and though you can't revisit it in the SUNNY ROUTE it's open again in the OMORI ROUTE, during ONE DAY LEFT.

Return to SPROUT MOLE VILLAGE and check out the front of SWEETHEART'S CASTLE. The hole in the stage has been boarded up, but you can still drop through it and find the LOST LIBRARY. This time around there are enemies, as well, so the whole party joins OMORI for the trip.

(Note that if you claim ownership of SWEETHEART'S CASTLE by speaking to the KEEPER OF THE CASTLE the entirety of the castle will be erased from existence. This includes the LOST LIBRARY. Be sure to fully explore it before wiping out SWEETHEART'S influence.)

While exploring the LOST LIBRARY you'll run into a variety of SOMETHING-style enemies, each labelled ???. These creatures appear in a few other places on ONE DAY LEFT, though there are more of them in LOST LIBRARY, and more varieties to boot. The ???s grant no EXP, CLAMS, or items upon defeat, and beyond seeing what they can do you're best off avoiding them all.

Aside from the enemies the LOST LIBRARY is the same as you left it until you reach the lowest level, to the south. Check to the left of the stairs and you'll find a beam of light. It'll take you into the same room that you probably found on your first trip through here, the one with the piano. If you inspect the northern wall you'll find three holes, and checking them will generate a hollow sound. Must be something behind them. There's also a save point in this room, so clearly there's more to it than meets the eye.

This little corner of LOST LIBRARY leads to three boss battles, each related to one of SUNNY'S fears. You've fought these creatures before, only this time the fights will be real. You can't get at them, however, until you make a trip to DEEPER WELL. Explore the area and you'll find three pieces of SHEET MUSIC, each of which will open a hole in LOST LIBRARY. The pieces of SHEET MUSIC are in the following locations:

  • Use the lower, eastern teleport pad when you reach the large platform that's not far from the entrance of DEEPER WELL. Head south in the next corridor to find another teleport pad. It'll take you outside to the SHEET MUSIC.
  • From the previous piece of SHEET MUSIC, take a right as you're heading back north. A teleport pad will take you outside to the second piece of SHEET MUSIC.
  • Return to the large platform mentioned earlier and use the northeastern teleport pad. Follow the path until it brings you to a cave that leads to the BRANCH CORAL you (hopefully) spoke to earlier in the game. Just outside the cave entrance is the last piece of SHEET MUSIC.

Return to the LOST LIBRARY once you have all three pieces of SHEET MUSIC and inspect the piano. Placing them on the piano will create beams of light by the holes, each of which leads to one of the aforementioned boss battles. We'll do them from left to right.


Ahh, the monster on the stairs. The battle against this SOMETHING begins with a ten-turn countdown, and if you can't defeat it before time runs out you'll automatically lose the battle. Other than that SOMETHING'S very presence makes everyone but OMORI AFRAID, and it can buff its own defences, debuff your party's offensive capabilities, and otherwise just do damage.

This SOMETHING doesn't do a ton of damage with its attacks, so you should prioritize going on the offensive. Use an AIR HORN to make everyone ANGRY rather than AFRAID, then double up on the ANGER with another AIR HORN or KEL'S MEGAPHONE SKILL. Jump between lowering SOMETHING'S defences - there are plenty of SKILLS and TOYS for doing this - and just plain doing damage as quickly as you can. So long as you're using multi-hitting SKILLS the fight shouldn't even come close to taking ten turns.

OMORI will learn the VERTIGO SKILL for defeating SOMETHING IN THE DARK.


Spiders! This SOMETHING is pretty basic, and will spend each turn attacking either one or all of your characters. Its offensive capabilities are extremely high, however, and at lower levels it can OHKO your party members if it lands a critical hit. Get unlucky when it attacks the whole party and you could be facing a total wipe.

Aside from lowering the SOMETHING'S defences - as well as outright attacking - the only thing you can really do here is lower the SOMETHING'S ATTACK stat. The fact that you can't change its EMOTION makes this more difficult, though OMORI'S STARE and VERTIGO SKILLS, as well as HERO'S SMILE and DAZZLE SKILLS, can be used to deaden the enemy's blows a bit. You can also increase everyone's defenses a bit by making them all SAD at the beginning of the fight, which will also get rid of that annoying AFRAID status.

OMORI will learn the CRIPPLE SKILL for defeating SOMETHING IN THE WALLS.


And, last but not least, water. The third SOMETHING is similar to the first in that you're facing a race to the finish line, though this time your team will be taking damage multiple times every turn. This SOMETHING will use a whirlpool attack to slow and drown your characters, and the drowning effect gets gradually worse as you do more damage to the SOMETHING. At the end of each turn you'll also take extra damage, similar to the battle against HUMPHREY. The SOMETHING has a lot of health, so you can easily find yourself unable to defeat it before it can kill your party.

Rather than rush through this fight you're best off prepping your team from the start. Use SKILLS that will lower the SOMETHING'S defenses until they can't go any lower, and get your whole party ENRAGED to maximize their damage. Then, once everybody is healthy and ready to go, unload your most powerful SKILLS on the SOMETHING, turn after turn. So long as everyone is doing around 500+ damage each turn you should easily chew through the SOMETHING'S HEART before it can really put on the hurt. Have HERO use SNACKTIME or KEL some good healing items if your HEART starts to run out before the enemy's - and keep in mind when doing calculations that even KEL will be slower than the SOMETHING as the battle rages on.


Defeating all three SOMETHINGS will earn you an achievement, and you'll be all but done in the LOST LIBRARY. Check the piano for one last little detail, then head back to the surface.