The expansion Hiroshima Lightning faced a 24-point deficit after 10 minutes on Friday night, and never recovered.
The visiting Shimane Susanoo Magic routed the Lightning 115-62 in the series opener in Hiroshima.
Shimane (9-6) controlled the boards from start to finish, out-rebounding the hosts 63-24.
Josh Davis paced the Susanoo Magic with a game-high 29 points and 21 rebounds (eight offensive). The San Diego State product leads the league with 15.7 rebounds per game.
Scootie Randall added 26 points for Shimane, including 10 of 11 at the free-throw line, and Wayne Marshall had 20 points and 13 boards. Jun Abe poured in 13 points and Tatsuhiro Yokoo had 11.
Hiroshima (1-12) trailed 63-24 at intermission.
Andre Murray led the Lightning with 20 points and Adam Herman had 16.
Hiroshima, guided by American bench boss Joe Navarro, extended its losing streak to seven games.