Serenade's secret

Serenade's secret

https://pbs.twimg.com/media/E4XawDXWEAsmluS?format=jpg&name=small

Serenade's secret
Serenade's discarded illustrations

What's the relationship between Serenade and Mamoru?
Urakawa Mamoru, who's interned in a hospital because he's got the same illness as Saito,
has Serenade's mark on his wheelchair.
Given how mamy Operators attach their Navi's mark on their clothes or belongings,
Serenade might have been Mamoru's own Navi.

Bottom left image: Serenade's setting image
Ears thickness: as thin as indicated here
Cross section: (too small to read)

Middle left illustration:
Left: (too small to read)
Right: cross-section triangle

Bottom left illustrations:
Warning about Serenade's hair
When the front hair flutters, the part hitting the helmet remains affixed
and most doesn't move
Which means it mustn't end up like this

TL by @Bapgei