Here is the full list of all 60 1bitHeart achievements.
Play the Extra Story
Befriend Mikado
Complete all friendships
Befriend Misane
Befriend Tobari
Befriend Kotora
Befriend Kirai
Befriend Nomiya
See the Happy End
Befriend Sagara
Befriend Meu
Befriend Izuchi
Befriend Saaya
Befriend Meru
Befriend Mary
Befriend Hitohito
Befriend Kirara
Befriend Ryuuri
Befriend Yuuto
Befriend Hiyu
Make 25 friends
Befriend Jin
Befriend Azusa
Befriend Enri
Befriend Asuto
Befriend Momori
Befriend Misato
Befriend Akashi
Befriend Sora
Befriend Moroku
Befriend Chino
Give someone chocolate for the first time
Befriend Rocca
Befriend Yukinaga
Befriend Akuta
Befriend Sekiyu
Befriend Nio
Befriend Sakuma
Befriend Kiri
Befriend Kuroku&Shiroro
Befriend Kaori
Befriend Shiren
Befriend Takamiya
Befriend Hakuhi
Befriend Shitara
Befriend Potete
Befriend Aira
Befriend Akitaka
Befriend Haruya
Befriend Miumi
Befriend Natsukage
See the Normal End
Befriend Yasune
Find the Cheat Code (bottom-right of Bit World...)
See the Bad End
Begin Chapter 4
Get GAME OVER
Begin Chapter 3
Begin Chapter 2
Begin Chapter 1