The Rising Of The Shield Hero is a Japanese light novel created by Aneko Yusagi which originally published as a web novel and later adapted into a twelve volume manga series by Aiya Kyū.
In a short interview with the author, Naofumi was inspired from a defence-specialised crusader character in “Ragnarok Online”.
Demi-Humans adapt to its most efficient form based on their levels. This is why Raphtalia’s body grew quickly in a span of a week. Her physical appearance may look mature but her mental maturity still remains as a 10-year-old.
Kaito Ishikawa, the voice actor of Naofumi, also voices over Tenya from My Hero Academia and Tobio from Haikyuu. While Asami Seto, the voice actress of Raphtalia, voices over Chihaya from Chihayafuru and Mai from Bunny Girl Senpai.
There’s a comedy spin-off story about the Spear Hero, Motoyasu Kitamura, called The Reprise of the Spear Hero.