Here is the full list of all 84 OMORI achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Reach the good ending.
Go to SEAN and KAREN's housewarming party.
Give FLOWERS to MARI.
High-five KEL three times.
Have a ghost party.
Commission ROCOCO.
Defeat UNBREAD TWINS.
Get the LOL SWORD.
Defeat HUMPHREY.
Defeat SLIME GIRLS.
Defeat PLUTO (EXPANDED).
Defeat MR. JAWSUM.
Battle the "bees".
Defeat SWEETHEART.
Perfectly train the SPROUT MOLE choir.
Kill the first SOUS CHEF.
Choose the SUMMER MOLE.
Ruin Christmas.
Complete ORANGE JOE's quest.
Turn the valve to the right in RAIN TOWN.
Defeat KITE KID.
RELEASE ENERGY on your foes.
Defeat THE EARTH.
Go to sleep after a long day.
High-five KEL.
Lose to KIM and VANCE.
Wake up in the morning.
Make your way and talk to LONE MOLE.
Defeat SPACE EX-BOYFRIEND.
Defeat DOWNLOAD WINDOW.
Defeat ???.
Fly the BUTT CERTIFICATE in CATTAIL FIELD.
Water a plant back to life in BASIL's garden.
Complete your TO-DO LIST.
Reach the bad ending.
Reach the other ending.
Get all rewards from the RECYCLING MACHINE.
Choose the SPRING MOLE.
Choose the FALL MOLE.
Choose the WINTER MOLE.
Watch all movies in SWEETHEART'S "throne room".
Defeat the CHICKEN? at the top of DINO'S DIG.
Trade CLAMS for CLEMS.
Pet all the creatures in MARINA's sector in HUMPHREY.
Hold 99 TOFU.
Defeat 100 BUNNIES.
Defeat 100 SQUIZZARDS.
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 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.
Complete the math worksheet correctly.
Complete the grammar worksheet correctly.
Pet a dog.
Feed the STRAY CAT every day and sunset.
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.
Complete the FOE FACTS! journal.
Listen to MR. SCARETHROW's rant.