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