A visitor holds a keyring at K-Illustration Fair at COEX in Gangnam District, Seoul, on Feb. 6. Yonhap

In a world of mass-produced goods, fashion has become more than just wearing the latest styles for trend-savvy Millennials and Gen Zers. Young consumers are redefining self-expression through personalization, driving a booming trend of decorating and customizing everything from diaries and keyboards to bags and desk spaces.

Known as "-kku," a suffix derived from the Korean word for decorating, the trend is sweeping through the younger generation, transforming everyday items into unique statements of identity. Driven by a desire for individuality and fueled by social media, it is reshaping consumer behavior and prompting major brands to introduce customizable options as a hands-on way of self-expression.

According to the big data research company KPR Insight Tree, interest in customization is steadily increasing. Mentions of customization online surged by 75.3 percent from January to August last year, rising from 233,274 to 408,986.

Asung Daiso's spring-themed decorative supplies / Captured from Daiso's Instagram

Diary decoration is one of the trends that triggered the customization phenomenon. Expanding beyond just keeping a record, diary decorating involves using ornamental stickers and masking tape when writing in a journal. Along with the entries, people often decorate the diary pages with related photos, drawings, and stickers to their liking, as well as create their own covers.

Decorating journals has become popular on YouTube, with people sharing tutorials for beginners on how to apply and arrange decorative supplies on diary pages, along with ASMR videos and reviews of decorative supplies.

"When I record memories in an analog way (in a diary), I feel like I can recall them more deeply. That's why I decorate things in my own unique style to make those memories more special and memorable," actress Jo A-ram said in a recent episode of the reality show "I Live Alone," sharing that she can spend hours on a single spot when she starts decorating her diary.

A photo of actor Jo A-ram's diary / Captured from MBC's YouTube channel

Along with diary decorating, adorning bags with various types of keychains and plushes, and customizing tumblers with stickers and keyrings have become another prevalent trend.

Lee Young-ae, a professor of consumer economics at Incheon National University, explained that the younger generation's appreciation for experiences led to the rise of the trend.

"(Millennials and Gen Zers) have characteristics that strongly value first-hand experiences and personal involvement. While previous generations focused on purchasing finished products, these generations prioritize the experience and the practical value as well as the usability of products," she said.

"As a result, rather than simply acquiring completed products, they're a generation interested in creating something uniquely their own when consuming a product and projecting their personal values onto objects, like things that exist specifically for them. They have (a) do-it-yourself (DIY) desire that stands out compared to other generations. It's not simply about purchasing expensive products for show, but rather about owning products that they've invested with value through personal experiences and processes that make them happy."

ABOE's plush keychain / Courtesy of ABOE

As the trend surges, demand for the decorative supplies needed for customization is growing, leading brands to respond with new releases.

According to the online platform 29CM, sales of high-end writing instruments like fountain pens, ballpoint pens and pencils grew by 240 percent this February compared to the same period last year. Diaries and planners increased by 64 percent and notebooks by 43 percent.

Sales of keyring products on the platform from October last year through January also surged by 178 percent compared to the same period the previous year. Plush keyrings saw a 28 percent increase, while mini bag-style pouch keyrings grew by 173 percent.

The platform is set to host its first in-person stationery fair, Inventario, in April, inviting a variety of brands and creators.

Distributor Asung Daiso is catering to the growing demand for diary decorating by offering MBTI-inspired personality stickers and character stamps, as well as DIY plush keychains for bag decorating enthusiasts. It recently rolled out spring-themed decorative supplies like cherry blossom patterned stickers and DIY rubber band keyrings.

Preflow's keyboard / Captured from Preflow's Instagram

Lifestyle brand JAJU has launched a promotion offering personalized initials embroidery with the purchase of its pajama set. The promotion garnered an explosive response after being temporarily offered last December, prompting the brand to officially launch the service.

Earlier this year, coffee franchise A Twosome Place launched its New Year's gift set, which includes a tumbler strap and holographic removable stickers, allowing consumers to personalize their tumblers with custom initials.

Building on the trend of customizing diaries and bags, people are now seeking to personalize other everyday items, such as keyboards.

Local shopping mall I'Park Mall held a keyboard festival last month, featuring around 20 brands offering various products for customizing keyboards, such as keycaps, covers and special edition models.

Lee noted that the customization trend will not only continue but is expected to expand to other everyday items.

"The items will change but the trend of creating something yourself through experience will continue … The fundamental appeal of DIY, spending time crafting something unique and of sharing it on social media will always be there, as specific trends might evolve," she said.

Diary cover made by Broccoli UD / Captured from Broccoli UD's Instagram

"This movement could expand beyond small personal items to larger-scale projects like home decoration, construction or even urban gardening."

She added that as the country's economy struggles with inflation, more people will seek ways to achieve self-sufficiency to avoid extra spending.

"Korea's DIY market, particularly in areas like interior design and self-construction, is still in its early stages. However, as labor costs rise, more people may consider taking on projects themselves, leading to a pattern of increase in related lecture courses, resources, and social media sharing," she said.

"In Western countries, rising labor costs have already driven a shift toward self-sufficiency in home improvement and crafting. What was once a niche hobby could become a widely accepted practice, transforming DIY from a decorative activity into a larger cultural movement centered on making and creating. As this market grows, there is significant potential for further development and sophistication in the DIY industry."