Wing Nel Metcalfe and hooker Moe Nagaoka exchanged tries in the opening 15 minutes before hooker Kelsey Jones and wing Amy Williams added to Wales' first-half haul.

In-form prop Sisilia Tuipulotu crossed after the break before Williams added her second in a rare move from the backs.

Wales were then reduced to 13 players with replacements Keira Bevan and Hannah Dallavalle both shown yellow cards, but dug defensively deep to keep the hosts out in the dying minutes.

Wales finish the Global Series with three wins, their only defeat coming against USA. It marks a complete transformation for Sean Lynn's side, who prior to the South Africa game had gone nine Tests without a win.

The Sakura Fifteen, meanwhile, are still waiting for their first victory since May and a first under head coach Toshizumi Kitagawa.

Wales, who ground out a 17-0 win in the opening Test, had the better of the early exchanges.

They were rewarded with the opening try after Japan's loose goal line dropout, which co-captain Alex Callender thundered up deep into the 22.

Tuipulotu then came close, before the ball was shipped to Metcalfe to finish in the corner. Lleucu George, preferred at 10 this week to Bevan, added the conversion.

The hosts then enjoyed a spell of pressure thanks to Wales' indiscipline and bagged their first try of the double header with hooker Nagaoka touching down from the maul.

Wales were back among the tries 10 minutes later with George's kick putting the defence under pressure and Lisa Neumann winning the turnover.

Wales rightly backed their lineout with Jones touching down for her second in as many games. George was again on target from the tee to extend Wales' lead.

Despite improved conditions this week, the visiting backline looked a little disjointed. Thankfully the maul was dominant and Japan could do little to stop it from gaining ground before Seren Lockwood found Williams in space on the wing.

Japan's indiscipline proved costly in the second half, with Jennifer Nduka paying the price for an accumulation of penalties with a yellow card.

It paved the way for Wales to cross for the try bonus-point, with Tuipulotu proving unstoppable from a metre out.

Wales continued to play through the forwards, with Callender working tirelessly in her new position of eight this week.

The backs eventually got in the action and it came from a huge Callender pass out wide to Neumann who fed the pacy Williams for her second run in of the evening.

Both sides emptied their bench soon after, and while Wales' bench proved the difference last weekend, it had the opposite effect this week, with the experienced Bevan and Dallavalle both shown yellow cards as the game entered its final 10 minutes.

Bevan had been penalised when Wales had been on a warning, while Dallavalle, making her first appearance in the competition, was given her marching orders for a blatant hair pull.

Japan threw everything at Wales in the dying moments, but could not take advantage of their numbers and it was fitting that Callender came up with the crucial turnover.

How they lined up

Replacements: Kuge, Mine, Fuji, M Nishimura, Korai, Seo, Ito, S Nishimura

Replacements: Reardon, Davies, E Jones, Aiono, Evans, Dallavalle, Bevan, De Vera.