October 3, 2017 vs Chunichi at Yokohama – Hosokawa hit a home run in his first game and plate appearance. The blast came with runners on first and third and two out in the first inning off Shotaro Kasahara. He is the sixty-first player in NPB history (one from the single league era, thirty-two Central League, twenty-eight Pacific League, and four Yokohama) to hit a home run in his first plate appearance. He is also the sixth player out of high school in the NPB history (first in Yokohama history) to accomplish the feat in his first year.
The other three Yokohama players: Dick Stuart in 1967, Stephen Randolph in 2009, and Tomo Otosaka in 2014.
The other five players out of high school: Morimichi Takagi on May 7, 1960; Nobuyuki Kagawa on July 8, 1980; Hiroyasu Hayashi on June 29, 1990; Hideki Saeki on September 24, 1990; and Taishi Hirooka on September 29, 2016.
October 28, 2017 vs Softbank at YafuOku Dome – Hosokawa recorded a single to center as pinch-hitter in the ninth inning and became just the second rookie out of high school in NPB history to record a hit in their first Nippon Series plate appearance. The other was Kimiyasu Kudoe in 1982 (Game 6).
Source: Nikkan Sports 10/29/2017