[3] In 2011, Arai co-starred as Detective Kazuhiko Soga in a one-off TV crime thriller Douki with co-stars Ryuhei Matsuda as Detective Ryota Udagawa and Chiaki Kuriyama as Michiru Soga.

The June 2012 issue of Switch, a Japanese arts and media magazine,[4] features a special segment on top ten manga that teaches love and passion, chosen by Japanese actors, artists and musicians including Arai, who chose Bakuman while explaining: "You should up your girl power by learning how to behave like a heroine.

[9] He had stated in a number of Japanese interviews that he has a continual interest in being involved with films that explore Korean-Japanese issues.

[10] On February 1, 2019, Arai was arrested for sexual assault involving rape of an outcall masseuse on July 1, 2018 by the Tokyo Metropolitan Police Department.

[17] On November 17, 2020, the sentence was reduced to four years in prison due to the actor paying a settlement of 3 million yen (about US$29,000) to the victim.