Successfully complete the indicated task to unlock the corresponding achievement.

Achievement	How to unlock
Been There, Done Bad	Seen the true bad ending.
Brothers in Arms	Seen the Amamiya brothers ending.
Murder Sea Wrote	Seen Yukinari's ending.
Seen Too Much	Unlocked all CGs.
Seventeen Again	Seen the secret ending.
Short End of the Stick	Seen Chiaki's ending.
Significant Brother	Seen Natsume's ending.
Star-Crossed Brothers	Seen Masaharu's ending.
Trial and Error	Found and used all mementos.