Akko draws a "hanamaru" on Naoto's documents. The hanamaru mark is a typical "well-done" mark that Japanese teachers at primary school draw on homework or tests that students do well on.
Based on the Japanese manga "Himitsu no Akko-chan" that was published in the 1960's and later turned into a cartoon.
The amusement park that they visit is the Arakawa yuenchi amusement park in north Tokyo.