Olivier Giroud and Ryo Miyaichi scored in the first half to lead Arsenal to a 3-1 preseason win over Japan's Nagoya Grampus on Monday.Giroud beat Nagoya goalkeeper Seigo Narazaki just three minutes in, converting a cross from Tomas Rosicky to give the visitors an early lead.Giroud was tripped in the box midway through the first half and local favorite Miyaichi doubled the lead from the penalty spot to the delight of the crowd at Toyota Stadium.Theo Walcott beat Narazaki in the 55th minute to make it 3-0 before Kisho Yano pulled one back for the hosts with a superb header that beat Arsenal goalkeeper Lukasz Fabianski in the 72nd.The match was a homecoming for Arsenal manager Arsene Wenger who managed Nagoya in 1995 and 1996.