Here is the full list of all 12 Happy Guy achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Crypto save their life.
Discover the secret of the nurse.
Take a screenshot and the story begin.
New house, new home, new relationship.
Life is not a dream.
Fasting come after feasting.
No way home.
New job with the naughty boss.
Run, Haro. Run...
Meet Akari for the first time.
Help Akari to build the restaurant.
Happy ending with Akari !