Ogasawara made his professional debut in July 2017 against Shoyo Yuasa, during the REBELS×IT’S SHOWTIME crossover event.[2] Ogasawara won the fight by unanimous decision.[3]
After a KO victory in Thailand a month later, Eisaku went on a six fight winning streak, beating Tatakau Pastry,[4] Naoya Yajima,[5] Yasuhito Furuta,[6] Yosuke Kafuji,[7][8] Dynamo Puchi,[9] and Kiminori Matsuzaki.[10]
His eight fight winning streak earned him a chance to fight Hiroyuki Yamano for the REBELS-Muaythai Flyweight title.[11] He defeated Yamano by unanimous decision.[12]
After winning his first major title, Ogasawara would suffer his first professional loss in the very next fight. He was scheduled to fight Ryuji Kato during TNK1 feat.REBELS,[13] and lost by KO in the first round.[14] Ogasawara was then scheduled to fight Hong Chunhen,[15] but once again lost by KO, after being dropped three times in the second round.[16]
Eisaku would rebound from these losses by winning his next five fights. He beat Rose Tatsuya and Satoshi Katashima by TKO,[17][18] and won decisions against Yasuhito Furuta,[19] Yun Dok Jae[20] and Jockylek GT-gym.[21]
He was scheduled to fight for the MuayThaiOpen Super Flyweight title during MuayThaiOpen 30.[22] Ogasawara won the fight by TKO in the second round, after knocking Takayuki down three times in the second round.[23] The two of them fought a rematch four months later, during REBELS.37, for the REBELS 52.5 kg title.[24] Ogasawara once again won by TKO, this time in the first round.[25]
Super bantamweight
ISKA and WPMF title wins
Ogasawara afterwards fought Yuko Ogata at BLADE.2,[26] and won the fight by a first round KO.[27] Eisaku then fought Munfan Acegym during Rebels 38,[28] and won by unanimous decision.[29] He scored knockout wins of Arashi Fujihara[30] and Takashi Ohno,[31] as well as a unanimous decision win over Taiki Naito.[32]
Ogasawara was scheduled to fight the former RISE Bantamweight champion Yuta Murakoshi during RISE 112.[33] Eisaku lost by a third round TKO.[34] It was his first loss in nearly three years.
He rebounded from his loss with a 43 second KO of Masahide Kudo.[35] Ogasawara won his next five fights by (T)KO as well, scoring victories over Keisuke Miyamoto,[36] Hiroya Haga,[37] Sung Ji Byun,[38]Wanchalong PK.Saenchai[39] and Hyo Sik Hwang.[40]
Ogasawara was set to fight Franck Gross for the ISKA K-1 rules World Bantamweight title. Ogasawara won the fight by a unanimous decision.[41] After a draw with Ryo Takahashi, Ogasawara fought Dawsakon Mor.Tassanai for the WPMF World Super Bantamweight title. He won the fight by a third round KO.[42]
KNOCK OUT Super Bantamweight tournament
He suffered his fourth professional loss to Rui Ebata during KNOCK OUT SURVIVAL DAYS. Ebata won their fight by KO.[43]
Eisaku fought in the Rajadamnern Stadium for the first time in August 2018, when he faced Jomkitti Sitanothai. He beat Jomkitti by a second round KO. He was then scheduled to fight King Kyosuke during Rebels 58,[44] and won by unanimous decision.[45] He rematched Ryo Takahashi during KING OF KNOCK OUT 2018, and won by unanimous decision.[46] Eisaku beat Petyaso Dabrunsarakarm by a head kick KO at the Pancrase REBELS Ring 1.[47] Eisaku extended his winning streak to five, with a decision win over Seiki Ueyama.[48] He lost to Yuki Kasahara by TKO, after the ringside doctor stopped the fight in the second round.[49]
Ogasawara entered the 2019 KNOCK OUT Super Bantamweight tournament. He won a unanimous decision against Mikel Fernandez in the semifinals, but lost a decision in turn in the finals, in a rematch with Rui Ebata.[50]
Rebels 55.5 kg tournament
After his loss in the tournament finals, Ogasawara was scheduled to fight Saoek Sitchefboontham.[51] Saoek won by a second round head kick KO.[52]
He won his next three fights, defeating Dekdoi TNmuaythai and Issei Saenchaigym by KO,[53][54] and defeating Kaopong Por.Petchmanee by decision.[55]
Ogasawara participated in the Rebels 55.5 kg tournament, facing Keisuke Miyamoto in the tournament semifinals. He won by majority decision. He is scheduled to face his brother Yukinori Ogasawara in the final for the inaugural REBELS-RED 55.5 kg title.[56] He was rescheduled to fight King Kyosuke for the KNOCK OUT RED Super Bantamweight title.[57] He won the fight with a body kick knockout, mid-way through the third round.[58]
KNOCK OUT RED Super Bantamweight champion
Ogasawara was scheduled to face the former DEEP KICK 57.5 kg champion Hiro Yokono in a non-title bout at KNOCK OUT 2021 vol.3 on July 18, 2021.[59] He won the fight by a second-round knockout. Both the knockout and the knockdown that preceded it were scored it the same manner, by low kick, which Ogasawara had been throwing throughout the bout.[60]
Ogasawara was scheduled to make his first KNOCK OUT title defense against Issei Saenchaigym at KNOCK OUT 2021 vol.6 on November 28, 2021.[61] He won the fight by unanimous decision.[62]
Ogasawara was booked to face Takuma Ota at KNOCK OUT 2022 vol.2 on March 12, 2022.[63] He won the fight by unanimous decision.[64]
Featherweight
Ogawasara vacated the Knock Out Red Super bantamweight title on August 18, 2022. On the same day, it was announced that Ogasawara would face Takeru for the vacant KNOCK OUT RED Featherweight title at KNOCK OUT 2022 vol.5 on September 23, 2022.[65] He won the fight and the vacant title by a second-round knockout.[66]
Ogasawara faced Chartpayak Saksatun at KNOCK OUT 2022 vol.8 on December 11, 2022.[67] Despite twice knocking Chartpayak down, Ogasawara lost the fight by a third-round technical knockout, as his opponent was able to open a cut above Ogasawara's eye midway through the final round.[68]
Ogasawara faced the three-weight Lumpinee Boxing Stadium champion Ronachai Tor.Ramintra at KNOCK OUT 2023 SUPER BOUT BLAZE on March 5, 2023.[69] He won the fight by unanimous decision, with scores of 29–28, 30–28 and 30–27.[70]
Ogasawara faced Tongmeechai Fellow Gym at KNOCK OUT 2023 vol.2 on June 11, 2023.[71] He won the fight by majority decision, with scores of 29–28, 30–29 and 29–29.[72]
Ogasawara faced Yodwittaya YiewBangSaen at ONE Friday Fights 30 on August 25, 2023.[73] He won the fight by knockout, 31 seconds into the opening round.[74]
Ogasawara faced Pansak Wor.Wantawee at KNOCK OUT 2023 vol.5 on November 5, 2023.[75]