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.
Defeat the PET ROCK champion.
Get a perfect score delivering PIZZA.
High-five KEL three times.
Brush your teeth every day.
Defeat HUMPHREY.
Defeat SLIME GIRLS.
Get the LOL SWORD.
Have a ghost party.
Trade CLAMS for CLEMS.
Commission ROCOCO.
Defeat PLUTO (EXPANDED).
Defeat MR. JAWSUM.
Defeat SWEETHEART.
Perfectly train the SPROUT MOLE choir.
Kill the first SOUS CHEF.
Hold 99 TOFU.
Ruin Christmas.
Choose the WINTER MOLE.
RELEASE ENERGY on your foes.
Defeat 100 BUNNIES.
Complete ORANGE JOE's quest.
Go to sleep after a long day.
High-five KEL.
Lose to KIM and VANCE.
Complete all part-time jobs once.
Wake up in the morning.
Defeat KITE KID.
Defeat SPACE EX-BOYFRIEND.
Defeat DOWNLOAD WINDOW.
Listen to MR. SCARETHROW's rant.
Defeat THE EARTH.
Defeat ???.
Gain BREAD using BREAD SLICE.
Make your way and talk to LONE MOLE.
Fly the BUTT CERTIFICATE in CATTAIL FIELD.
Pet a dog.
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 SUMMER MOLE.
Choose the FALL MOLE.
Watch all movies in SWEETHEART'S "throne room".
Turn the valve to the right in RAIN TOWN.
Defeat the CHICKEN? at the top of DINO'S DIG.
Pet all the creatures in MARINA's sector in HUMPHREY.
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.
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.
Take $20.00 from KEL's wardrobe.
Quit in the middle of a part-time job.
Complete the math worksheet correctly.
Complete the grammar worksheet correctly.
Feed the STRAY CAT every day and sunset.
Defeat the HOOLIGANS with PEPPER SPRAY.
Battle the "bees".
Insert every song into GINO'S JUKEBOX.
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.