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