Last updated: Aug 14, 2022
Airline (Japanese domestic): Japan Airlines (JAL). Their "Class J" (premium economy) seats are comfortable and very good deals.
Bookstore (offline): Junkudo Ikebukuro Main Store, Book 1st Shinjuku Store, and Maruzen Marunouchi Main Store (Japanese only). They have more than one million books, so I am looking forward to exploring them.
Convenience store (Japanese domestic): Seven-Eleven Japan (Japanese only). They provide the finest services and the most delicious foods in Japanese convenience stores.
Copy and print (Japanese domestic): Multi-function printer at Seven-Eleven Japan (Japanese only). You can pay not only with cash, but also with nanaco, a rechargeable electronic money card issued by Seven-Eleven Japan. I rarely print documents, so I don't have printers.
eBook: Kindle (Amazon). I have used it from 2013. Amazon is the largest eBook store, so I think they will continue providing their services for a long time.
Email: Gmail (Google). I have used it from 2007. It had the finest spam filter (Now spam filters of other email services work as well as Gmail's). Lately, I send few email message.
Home delivery (Japanese domestic): Yamato Transport. They provide the finest services.
Hotel booking site (Japanese domestic): Rakuten Travel. You can check availability of almost all hotels in Japan with it and Jalan.
Instant messaging: LINE, the largest instant messaging service in Japan.
Internet auction (Japanese domestic): Yahoo! Auctions Japan, the largest Internet auction service in Japan.
Online storage: Dropbox and Google Drive. Both provide their services for a long time, so I trust them. I pay for Google Drive and backup several TB of files on it, not on local HDDs. Now managing local HDDs is a hard job. Furthermore, data on local HDDs may lost easily.
Online household accounting book: MoneyForward (Japanese only). It records deposits and withdrawals by your credit cards. I am frustrated with their really slow PC site.
Online shopping: Amazon.co.jp and yodobashi.com. They deliver product very fast. You should order small amount of inexpensive products from yodobashi.com.
Taxi: Go and Uber. Go is the most famous app for taxi riding in Japan. Note that all the Japanese Uber drivers are professional limousine taxi drivers. The fees are a bit more expensive than ordinary taxis'. Both Go (slide-door) and Uber cars rarely reek of tobacco.