Shizuku began as a raindrop sprite formed from a cloud's single droplet, originating in the Shizuku Forest that shares its name. This character consistently celebrates a birthday on April 29th across all media.

Physically, Shizuku manifests as a simple blue raindrop equipped with light yellow wings. Experiencing happiness triggers the generation of rainbows from its forehead. Shizuku commands water-based abilities, controlling various water types, evidenced when manipulating a waterfall to save a friend. Forceful impact can temporarily transform it into a puddle, though it rapidly recovers its normal shape. Exposure to rain causes significant size expansion, likely through absorbing surrounding raindrops.

Its personality is perpetually cheerful and playful, frequently smiling even amid troubles. Shizuku exhibits daydreaming tendencies, sometimes appearing spaced out or acting unusually; fellow raindrop sprites note its "head in the clouds." This vibrant nature fuels significant popularity within the Shizuku Forest community.

Shizuku's family includes parents named Ametaro (father) and Rainy (mother), plus a sister called Ame-chan. Early franchise material referenced the character as Amesuke-kun, a name still visible on some merchandise.

Key relationships involve numerous Shizuku Forest inhabitants. Closest companions are Uruoi-chan (a skin lotion or pink lemonade sprite), Mirumiru-chan (a milk sprite), and Tsumorin (a snail). Uruoi-chan harbors romantic feelings for Shizuku, demonstrated when her kiss breaks Shizuku's frozen state, with Shizuku reciprocating a minor crush. The character also interacts with diverse sprites representing substances like nasal mucus, sweat, tears, and tea.

In the spin-off "NiJiRo Fairy Shizuku-chan," Shizuku adopts a human guise featuring blue hair and a sailor suit adorned with a brooch resembling its original raindrop face. This adaptation places the character in new narratives while preserving core identity elements.