Riku of the group NiziU brought laughter as her ambitious 5-year diary was stained with a "dark history" from the very first page.

On the 15th, the "NiziU 2025 FNS Music Festival Behind" video was released on NiziU's official YouTube channel, capturing Riku chatting with members in the waiting room.

On this day, Riku told the members, "I'll tell you something funny," and shared the news that she recently bought a thick diary that can be used for 5 years. The date she started writing the diary was December 6th.

However, Riku confessed, "The content of the beginning of December 6th was 'Today's reflection: The day I lost (left behind) my wallet,'" turning the scene into a sea of laughter. The mistake of leaving her wallet in Korea ended up decorating the first page of her 5-year diary.

In response, the members teased Riku, saying, "Do you have to look at that content every year for 5 years?" and "Everyone at the company knows," but also sent cheerful support, saying, "Try writing hard for 5 years".

Fans reacted with amusement, leaving comments such as "December 6th will be a day of suffering for 5 years," "The first page is intense," and "It's a cute mistake."

Meanwhile, the video released that day attracted attention by featuring not only Riku's diary episode but also the nervous appearance of members preparing for BoA's 'Merry-Chri' cover stage and their heartwarming teamwork encouraging each other.