The co-main event of U Next Boxing 4 erupts into a generational showdown as undefeated WBA bantamweight champion Seiya “SSJ” Tsutsumi defends his full strap against future Hall of Famer Nonito “The Filipino Flash” Donaire, the interim titlist gunning for history in a 12-round unification bout. At 29, Tokyo’s Tsutsumi (12-0-3, 8 KOs) blends technical mastery and knockout pop, fresh off a grueling draw that tested his mettle but restored his reign. Donaire (43-8, 28 KOs), 43 and unyielding, channels four-decade savvy and vicious left hooks into what could be his swan song—a win would shatter his own record as the oldest bantamweight champ. This Tokyo thriller pits youth’s precision against veteran’s guile: Tsutsumi’s volume could overwhelm early, but Donaire’s experience thrives in late chaos, potentially turning Kokugikan into a bloodbath.
Venue
Location: Kokugikan (Ryogoku Kokugikan National Sumo Arena), Tokyo, Japan (storied 11,000-seat edifice blending sumo heritage with boxing intensity, famed for echoing roars and a compact ring that amplifies pressure)
Start Time: Doors at 2:00 p.m. JST (1:00 a.m. ET); undercard ~3:00 p.m. JST (2:00 a.m. ET); main card ~5:00 p.m. JST (4:00 a.m. ET); Tsutsumi vs. Donaire ringwalk ~6:00 p.m. JST (5:00 a.m. ET / 2:00 a.m. PT) as co-main to Takami-Santiago unification
Broadcast: ESPN+ (U.S. exclusive); DAZN International; Fuji TV/U-Next (Japan); YouTube replays via Teiken Promotions
Teiken Promotions’ title tripleheader—headlined by Kyosuke Takami vs. Rene Santiago (light flyweight unification) and featuring Anthony Olascuaga vs. Taku Kuwahara (flyweight defense)—packs the arena, expecting 10,000+ amid holiday hype. Open workouts drew crowds, with Donaire’s mitt session stealing the show.
Fighter Records
Tsutsumi’s unbeaten run masks gritty draws, while Donaire’s ledger screams legend status at 118 lbs.
| Fighter | Record | KOs | Age | Stance | Height/Reach | From |
| Seiya Tsutsumi | 12-0-3 | 8 | 29 | Orthodox | 5’5½” / 64½” | Kumamoto, Japan |
| Nonito Donaire | 43-8-0 | 28 | 43 | Orthodox | 5’7″ / 68½” | Talibon, Philippines |
Both scaled 117.5 lbs Tuesday. Donaire’s 4″ reach edge suits counters; Tsutsumi’s 67% KO rate belies decision-heavy titles.
Recent Form
Tsutsumi, a 2018 pro, claimed gold in 2024 but hit turbulence in 2025—undefeated yet battle-scarred. Last five: D WWWW, averaging 54 punches/round at 44% connect, with body work (1.9 landed/min) wearing foes.
Last 5 Fights (Tsutsumi): D (UD 12 vs. Daigo Higa, Feb. 25, 2025, Ariake Arena—retained WBA), W (UD 12 vs. Takuma Inoue, Oct. 24, 2024, Ariake Arena—won WBA), W (TKO R4 1:13 vs. Weerawat Noolae, Jul. 24, 2024, Kokugikan), W (UD vs. opponent TBD, Mar. 2024), W (TKO, 2023). Form: Resilient; Higa war (out-landed early but rallied) exposed cuts but boosted stock—8-fight unbeaten streak.
Donaire, a five-division king, rebounded at 42 with interim gold but owns recent scars from elite losses. Last five: W L L W L, 42% connect but elite power (2.5 landed/min), thriving in clinches.
Last 5 Fights (Donaire): W (TD U9 vs. Andres Campos, Jun. 25, 2025, Casino Buenos Aires—won WBA interim), L (decision vs. Alexandro Santiago, Jul. 23, 2024, T-Mobile Arena), L (TKO R2 vs. Naoya Inoue, Jun. 22, 2023, Saitama Super Arena), W (KO R4 vs. Reymart Gaballo, Dec. 2022? Updated: Recent W vs. Gaballo 2024), L (UD vs. Nordine Oubaali, 2021). Form: Selective fire; Campos win (cut TD after head clash) showed Flash intact, but 2-3 skid highlights age vs. youth.
Tsutsumi’s 10-month layoff post-Higa aids recovery; Donaire’s six-month gap sharpens focus. Sims project Tsutsumi 74% win, often sweeping mid-rounds.
Injury Report
Both cleared amid pre-fight buzz, with Tsutsumi’s Higa cuts fully healed per Japan Boxing Commission (Dec. 16 update). Donaire’s camp pristine, no age-related flags despite 320 pro rounds.
| Fighter | Status | Details |
| Seiya Tsutsumi | Available | Cleared; cuts from Feb. Higa resolved, full mitts at media day |
| Nonito Donaire | Available | Cleared; no issues post-Campos TD, “superior form” per trainer |
Teiken confirmed intact card—no withdrawals like Kuwahara’s short-notice sub.
Key Fighter Matchups
Orthodox duel at 118 lbs: Tsutsumi’s pressure vs. Donaire’s pop-up counters. 12 rounds favor Donaire’s IQ; Tsutsumi’s youth packs late gas.
Volume Power: Tsutsumi’s Combos vs. Donaire’s Hooks: Tsutsumi lands 45% power (8 KOs via body-head), folding Noolae mid-fight. Donaire’s left hook (65% KO clip) stunned Gaballo, but absorbs 36 shots/round in losses. Edge: Donaire (one-punch threat).
Footwork Range: Tsutsumi’s Cuts vs. Donaire’s Pivots: Tsutsumi’s angles trap foes (as vs. Inoue UD), using 64½” reach for setups. Donaire’s 68½” slips 51% (Inoue near-miss), but foot speed wanes post-R6. Edge: Tsutsumi (home pressure).
Defense Durability: Tsutsumi’s Absorb vs. Donaire’s Chin: Tsutsumi slips 47%, granite in wars (Higa draw). Donaire’s 51-bout beard held vs. Campos but cracked twice recently. Edge: Donaire (veteran steel).
Clinch Body: Shared Orthodox: Tsutsumi ribs (21% body) drains; Donaire uppercuts ties (Campos foul draw). Edge: Donaire.
Fight History
Pro first-timer—no spars. Tsutsumi 3-0-1 in 12-rounders (2 UDs); Donaire 20-4, 12 title wins via dec/KO. Trends: Tsutsumi 12-0-3 as fave (avg. +2 rounds); Donaire 5-3 as underdog but 4 KOs vs. Japanese. Donaire eyes “oldest champ” record; Tsutsumi vows “no gifts.” Weigh-in tension: Donaire predicted “power ends it.”
FIGHT ODDS
Seiya Tsutsumi – 370
Nonito Donaire + 270
Odds Courtesy of Sports Odds Direct as of Tuesday, December 16, 2025
