Here is the full list of all 26 Nightshade achievements.
Unlocked all Achievements
Completed all Movies
Completed all Memoirs
Unlocked all CG's of Koga
Completed all CG graphics
Unlocked all CG's with Gekkamaru
Completed all Endings
Bad ending with Gekkamaru
Happy ending with Gekkamaru
Unlocked Gekkamaru Route
Unlocked all CG's with Kuroyuki
Bad ending with Kuroyuki
Happy ending with Kuroyuki
Unlocked all CG's with Goemon
Bad ending with Goemon
Happy ending with Goemon
Unlocked Goemon Route
Unlocked all CG's with Chojiro
Bad ending with Chojiro
Unlocked Chojiro Route
Happy ending with Chojiro
Unlocked Kuroyuki Route
Unlocked all CG's with Hanzo
Bad ending with Hanzo
Happy ending with Hanzo
Unlocked Hanzo Route