Here is the full list of all 20 STAY COOL, KOBAYASHI-SAN!: A RIVER CITY RANSOM STORY achievements.
All skills acquired for every character.
Collect all equippable items.
Receive Ending B.
Trade out an equipped item for the first time.
Receive Ending E.
One character has all skills at level 5.
Receive the True Ending.
Clear the game within 30 minutes.
Ride a UFO outside the UFO Shooting Stage.
Replay the game for a second time.
Obtain one character skill.
Clear the game once.
Defeat a big boss.
Become friends with Ryuji.
Take out one mid-boss.
Take out a Moyakun.
Defeat an enemy with a level 3 special attack.
Choose a pursuit attack.
Play as Kunio
Play as Mizoguchi