That someone was Samurai Japan coach Nobuhiro Matsuda, long time Fukuoka Softbank Hawk (and brief Yomiuri Giant). Matsuda had a post-home run routine of thrusting his right arm in the arm and yelling "Atsuo!" or "Hot Man!". He and Ohtani were doing the same routine to celebrate Suzuki's home run.
Here's a card for Matsuda's schtick from the "Nickname Catchphrase" insert set from the 2024 BBM Professional Baseball 90th Anniversary set (#NC12):
