The nine-year-old royal had cut back on classes after suffering anxiety attacks and stomach aches brought on by a series of incidents which included “rough behavior” by boys at her school back in March.
She has attended Gakushuin Primary School in Tokyo's Shinjuku Ward only sporadically over the past nine months but her worried parents now believe the youngster has turned a corner.
Princess Masako – whose royal duties have been reduced as she accompanies her only child with Crown Prince Naruhito to school – said in a statement: “Her hours in school are getting longer, and I am relieved to see her enjoy spending time together with her friends.
“It was due to rough behavior of boys in her grade.”
The royal medical team has also confirmed to the Japan Times the young princess is still receiving treatment for a stress-induced illness but is “steadily improving”.
As well as problems in school, the royal schoolgirl also received online death threats earlier this year.
Police in Japan arrested Kengo Ezaka, 26, in May for threatening to have "her head smashed with a hammer".
The year before, Aiko’s mother admitted to suffering from her own long-term stress problems.
She said: "I would like to continue my efforts to recover, with the help of people around me.
"Under the guidance of my doctor, I have been doing my best, step by step, to regain my health, mentally and physically."
