I do always wonder, what's the originality of Satori wearing backpack? Just kind of curious because Satori nendoroid got backpack as accessories but on canon game I never saw her using any

Xinser said:

I do always wonder, what's the originality of Satori wearing backpack? Just kind of curious because Satori nendoroid got backpack as accessories but on canon game I never saw her using any

From what I know, its because of a pun and joke that can be made from her name.

Touhou Wiki said:

Due to her ability to read minds, and the similarity of her "third eye" to Backbeard of "You damned dirty lolicon!" fame, a growing joke among fan artists depicts Satori as cognizant of (and disgusted by) lolicon.
Similarly, it has become common in fan art to break down the kanji of "Satori" (悟) into its component radicals (小五口) and add the katakana リ, spelling out "shougorori", read as "fifth-grade elementary student loli". Her apparently small stature in her portrait seems to add to this. It is thus not uncommon to see her depicted wearing a Japanese elementary-schooler's book satchel on her back.

Kalarz said:

From what I know, its because of a pun and joke that can be made from her name.

Ahh now that make sense, thank you!