Fortunately, there is various Mosquito repelling products sold at local drug stores and to help you keep mosquitoes to stay away. The product is called Ka-tori-ki 蚊取り器 for insecticidal products or Mushiyoke 虫除け for repelling products.
For repelling products, the recent popular devices are non-electrical ones, which help keep mesquites stay away or kill them by just using (spraying) in a room for one time, that would work for 12 hours. This types of devices are sold at drug stores.
Mobile types of mosquito-repelling/killing devices are also sold at drug stores. They are so convenient when you go to bushy places in Tokyo. It is called Keitai-Yo 携帯用 means "For mobile". There are mosquito-repellents that you put on your body. Spray types are called Mushi-yoke-spray 虫除けスプレー, and location types are called Mushi-yoke Cream 虫よけクリーム. If your skin is not too sensitive, it will be easier to protect yourself using Ka-tori-ki or Keitai-Yo Katori-ki.