The Boy (ボウイ) effect may hint at Sonoko being transgender or genderfluid.
The way one obtains the Minus Screwdriver (マイナスドライバー) effect implies that Sonoko had hurt someone she loved.
The visuals of the Mini Dress (ミニドレス) effect seem to imply Sonoko is being lewd or flirty. The way it is obtained refers to something she shouldn't be doing and possibly a loss of innocence.
The picture that allows one to obtain the Minus Screwdriver (マイナスドライバー), the figure from which you obtain the Music Box (オルゴール) effect, and the girl in the hospital bed (nicknamed Kinpatsu-san by fans) are speculated to be the same person.
Sonoko is suspected to be in love with or dating Kinpatsu-san. She is perhaps taking the train to visit her partner in the hospital.
The change in the expression of the girl who gives Sonoko the Odango (お団子) effect hints that Sonoko is trying to fit in as to not be mocked.