Whanganui's Chris Back is the manager of the squad.
The Japan A side have played two games in New Zealand and won them both.
Horrocks returns to the field where he won the 2017 Meads Cup final last October, with a handful of his Horowhenua-Kapiti opponents from that match also filling out the Development XV bench today.
It is a well-deserved callup for the Wanganui veteran, who has played 51 first class games for the province, receiving his blazer last year.
He debuted in 2013 against King Country and has played every Heartland match and Ranfurly Shield challenge since - either as the starting No9 or off the bench.
He represented the New Zealand Heartland XV in 2015-16.
Kick-off at Levin is 5.30pm.