Tetta Seki

Tetta Seki is a Japanese singer and actor, best known as a vocalist for the five-member dance and vocal group ONE N' ONLY. With his warm stage presence and distinctive red member color, he has built a dedicated following among J-pop and J-drama fans alike.

As of 2026, Seki continues to perform with ONE N' ONLY while expanding his acting portfolio with roles in films and television. His recent work includes leading parts in the "Battle King!!" film series, and he's slated to appear in the upcoming 2025 installment. Fans appreciate his versatility, from high-energy concerts to nuanced dramatic performances.

Beyond the stage, Seki is known for his approachable personality, creative hobbies like painting and hair styling, and his love for karaoke, where he holds VIP status. He remains one of the more visible members of ONE N' ONLY, frequently appearing in variety shows and fan events. [edit]

Tetta Seki was born on November 24, 1997, in Kanagawa Prefecture, Japan. Growing up in the greater Tokyo area, he developed an early interest in music and performance. As a teenager, he honed his skills in dance and vocals, dreaming of a career in entertainment.

His path to stardom began when he joined the talent agency Stardust Promotion, becoming part of their EBiDAN (Ever Blooming Idol Network) project. Within EBiDAN, he first performed as a member of the unit EBiSSH, where he gained valuable stage experience and began building a local fanbase.

Before his official debut with ONE N' ONLY, Seki also dipped into acting. In 2017, he landed a guest role in the drama "Sakura no Oyakodon," marking his first on-screen appearance. This early exposure to both music and acting would shape his dual career path.

His time in EBiSSH was formative, teaching him the rigors of idol life and preparing him for the bigger stage that would come with ONE N' ONLY's formation. He also developed his signature style and stage presence during these early years, traits that would later make him stand out in the group. [edit]

Tetta Seki's breakthrough came with the formation of ONE N' ONLY, where he took on the role of vocalist. The group debuted with a fresh sound that blended pop, rock, and electronic elements, quickly gaining traction in the Japanese music scene. Seki's powerful yet smooth vocals became a key part of their identity.

Alongside his music career, Seki pursued acting with growing seriousness. In 2019, he made a guest appearance in the drama "JOKERxFACE," adding to his television credits. His film debut came with "Battle King!!: We'll Rise Again" (2023), where he played Sanada Shinsaku, a role that showcased his action capabilities.

He followed that with a part in "100 Byo no Keno: Kenka Battle Royale" (2024), playing Washida Ryu. These roles demonstrated his range and helped him build a reputation as a promising young actor. He's set to continue this trajectory with "Battle King!! Map of the Mind Part 1," slated for 2025.

Within ONE N' ONLY, Seki has also contributed to the group's variety content and live performances, often taking on MC duties and engaging with fans through social media. His solo activities, including modeling and appearances in magazines, have further solidified his presence in the entertainment industry. [edit]

Tetta Seki is perceived as the charismatic and approachable member of ONE N' ONLY. His energetic stage presence and warm interactions with fans have earned him a reputation as the group's mood maker. On social media, he often shares behind-the-scenes moments, personal thoughts, and his latest artistic endeavors, giving fans a glimpse into his life.

His fashion sense is another aspect of his image; he's known for mixing casual streetwear with more polished looks, and he occasionally styles his own hair, a talent he's proud of. Fans admire his authenticity, as he isn't afraid to show his quirky side, whether it's his love for Dragon Ball or his competitive streak in games.

Media coverage often highlights his versatility, pointing to his dual career in music and acting. He's seen as a rising star with a bright future, and his fanbase, though not as massive as some, is highly engaged and loyal, supporting him across all his projects. [edit]

Tetta Seki maintains a steady presence within the J-pop and J-drama landscape as a vocalist for ONE N' ONLY, drawing a dedicated following through his distinct red member color and versatile performances. While his fanbase is active across social media platforms where he shares behind-the-scenes content and personal thoughts, current records do not document a formal or official name for his supporters. The audience is characterized by an appreciation for his approachable personality and his ability to balance high-energy stage presence with nuanced dramatic roles in film and television. Unlike some peers who have sparked viral folklore or organized large-scale public campaigns, Seki's reputation rests on consistent output rather than singular legendary incidents. As of August 2026, iFANN has not yet collected sufficient data to assign a global ranking to Tetta Seki. Consequently, no placement figure is available at this time, and the subject remains unevaluated within the current scope of the index.[edit]

One of the more unexpected talents displayed by Tetta Seki is his proficiency in hand-pushed sumo, a playful skill he has showcased during variety show appearances. He is also recognized as a skilled impersonator, often entertaining friends and fans with accurate impressions. Seki shares a devoted interest in Dragon Ball with fellow ONE N' ONLY member Rei, a bond that frequently surfaces in fan interactions. His MBTI personality type is ENFP, a classification fans often cite as the source of his energetic and sociable nature. Known for his love of shopping, he regularly updates his wardrobe with trendy pieces. In the realm of karaoke, Seki holds VIP status at a local establishment, a detail that amuses his followers. He also enjoys watching movies and playing billiards during his downtime.[edit]

Tetta Seki keeps his family life relatively private, but he has mentioned in interviews that he grew up in a supportive household in Kanagawa. His parents encouraged his artistic pursuits from a young age, fostering his love for music and performance.

He has not publicly shared details about siblings, but he often speaks fondly of his family during fan events, expressing gratitude for their support throughout his career. His close bond with his mother is occasionally hinted at in his social media posts.

As of now, Seki lives alone, focusing on his career. He has mentioned that he enjoys having his own space, which allows him to pursue his hobbies like painting and listening to music late into the night. [edit]

Tetta Seki is closely associated with his group ONE N' ONLY, with whom he has performed and recorded since its formation. He also shares a bond with fellow member Rei, bonding over their mutual love of Dragon Ball.

Within the entertainment industry, he has worked with director and cast of the 'Battle King!!' series, building connections that could lead to future collaborations. His agency, Stardust Promotion, has been a constant support throughout his career. [edit]

Tetta Seki has kept his romantic life largely out of the public eye. There have been no confirmed relationships reported in the media or by official sources. He has not been linked to any fellow celebrities or public figures.

As of 2026, Seki is reportedly single, focusing on his career and personal growth. He has expressed in interviews that he is dedicated to his work and enjoys spending his free time on hobbies like painting and karaoke.

Given his rising fame, it's possible that future relationships may come to light, but for now, he remains unattached and private about his personal life. [edit]

Per iFANN's editorial analysis, Tetta Seki's net worth is estimated at $2 Million as of 2026. His income primarily derives from his activities with ONE N' ONLY, including album sales, concert tours, and merchandise. The group's popularity in Japan and parts of Asia has provided a stable revenue stream. In addition to music, Seki earns from his acting roles in films and television. While his filmography is still growing, each project adds to his financial portfolio. He also benefits from endorsement deals and appearances on variety shows, which are common for Japanese idols. His net worth has steadily increased over the past few years, thanks to the group's consistent output and his expanding solo work. As he takes on more prominent acting roles and potential solo projects, his earnings are expected to rise further.[edit]