The Zimbabwean fell to a 6-0 6-0 defeat in a second-round match that took just 36 minutes.
Mharakurwa said afterwards: 'I feel good. I played calmly and I gave him a bit of trouble. The difference is he makes every ball count.
'He's still trying after two, three balls and he doesn't give you a chance to wind it up. He doesn't give you a chance in the end. He takes control.'
Elsewhere in the men's competition, another Japanese player, five-time Paralympian Satoshi Saida, suffered a surprise defeat to rookie Adam Kellerman of Australia as he went down 6-3 6-2.
In the first round of the Quad Singles, Peter Norfolk of Great Britain - the world number three - started his campaign for a third Paralympic gold with a routine win over Japan's Mitsuteru Moroishi.
After winning 6-0 6-0, he said: 'I was nervous but the crowd were great. It's a nice feeling and a lovely atmosphere, and that's all thanks to the crowd. I enjoyed the match.
'I am concentrating on one match at a time. I know that the next one will be tough, but I am looking forward to the challenge of each match. It's a tough draw and potentially we could have an all-British final.'
Despite the apparent ease of his win, Norfolk said Moroishi was a challenge, adding: 'I played him in Japan and he is a very strong and difficult player.
'He plays with a good spin. If it was windier and he had the wind with him, I would have found it difficult. In this court the wind changes direction quite a bit.'
In the Quad Doubles, Beijing 2008 silver medallist Shraga Weinberg of Israel and new partner Noam Gershony beat Anders Hard and Marcus Jonsson of Sweden 6-1 6-4.
They joined Japanese pair Moroishi and Shota Kawano in the semi-finals after they proved too strong for Marco Innocenti and Giuseppe Polidori 6-3 7-6.
They were joined by USA pair Nick Taylor/David Wagner and Great Britain's Norfolk/Andy Lapthorne who had byes.