Here is the full list of all 84 OMORI achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Defeat DOWNLOAD WINDOW.
Complete your TO-DO LIST.
Reach the bad ending.
Reach the other ending.
Water a plant back to life in BASIL's garden.
Fly the BUTT CERTIFICATE in CATTAIL FIELD.
Get all rewards from the RECYCLING MACHINE.
Get the LOL SWORD.
Choose the SPRING MOLE.
Choose the SUMMER MOLE.
Choose the FALL MOLE.
Choose the WINTER MOLE.
Watch all movies in SWEETHEART'S "throne room".
Perfectly train the SPROUT MOLE choir.
Complete ORANGE JOE's quest.
Turn the valve to the right in RAIN TOWN.
Defeat the CHICKEN? at the top of DINO'S DIG.
Trade CLAMS for CLEMS.
Have a ghost party.
Pet all the creatures in MARINA's sector in HUMPHREY.
Hold 99 TOFU.
Defeat 100 BUNNIES.
Defeat 100 SQUIZZARDS.
Commission ROCOCO.
Commission all of ROCOCO's art.
Commission all of GATOR GUY's statues.
Let the plastic fish finish its song.
Take the KEEPER OF THE CASTLE's power.
Get the FLOWER CROWN from BASIL.
Recover at all of MARI's picnics.
Visit all mirrors.
Look through all telescopes.
Gain BREAD using BREAD SLICE.
Defeat ???.
Defeat THE EARTH.
Defeat UNBREAD TWINS.
Defeat SPACE EX-HUSBAND.
Defeat PLUTO and THE EARTH.
Defeat ROBOHEART.
Defeat MUTANTHEART.
Defeat PERFECTHEART.
Beat the BOSS RUSH.
Defeat every SOMETHING at the bottom of the LOST LIBRARY.
Don't high-five KEL.
Brush your teeth every day.
Take $20.00 from KEL's wardrobe.
Complete all part-time jobs once.
Get a perfect score delivering PIZZA.
Quit in the middle of a part-time job.
Go to SEAN and KAREN's housewarming party.
Complete the math worksheet correctly.
Complete the grammar worksheet correctly.
Pet a dog.
Feed the STRAY CAT every day and sunset.
Lose to KIM and VANCE.
Defeat the HOOLIGANS with PEPPER SPRAY.
Insert every song into GINO'S JUKEBOX.
Defeat the PET ROCK champion.
Defeat the RECYCLEPATH.
Throw away something.
Receive all FLOWERS in the hospital.
Read all the tombstones in the... dev room...
Enter code: haveadollariguess at www.omocat-shop.com for $1.00 off.
Unlock all achievements. Thank you for playing OMORI.
Give FLOWERS to MARI.
Complete the FOE FACTS! journal.
Listen to MR. SCARETHROW's rant.
Reach the good ending.
High-five KEL three times.
RELEASE ENERGY on your foes.
Defeat HUMPHREY.
Defeat SLIME GIRLS.
Defeat KITE KID.
Defeat PLUTO (EXPANDED).
Defeat MR. JAWSUM.
Battle the "bees".
Defeat SWEETHEART.
Kill the first SOUS CHEF.
Ruin Christmas.
Go to sleep after a long day.
High-five KEL.
Wake up in the morning.
Make your way and talk to LONE MOLE.
Defeat SPACE EX-BOYFRIEND.