I get the impression that a lot of Japanese wives would be fine with an open marriage, so long as there are certain ground rules (e.g., no divorce, no embarrassment, no flaunting the FBs, no STDs, etc.) and so long as it's mutual, meaning that the wife can play around too. I say this because for so many Japanese women, marriage appears to be more of a practical arrangement than a soul-mate-matchup. Also, nearly all of them are resigned to the fact that their husbands can use prostitutes if they want to (they'd pretty much have to be resigned to it, since the culture they live in essentially condones prostititution) and the idea of hubby having a FB or two or three is not too different from the idea of hubby screwing a Filapina or two or three.
Especially after a marriage hits the three-to-five year mark, when the woman usually loses interest and starts wanting to have sex with other men, proposing (or declaring) an open marriage is something to seriously consider. The wife's biggest fear often will be that the husband will leave, so if she receives ample reassurance on this point, it could work, I bet.
That said, if you want to keep things secret, there are lots of apps out there that
look like a calculator or some other kind of app, but that can be unlocked by the entry of a secret code and that contain functionality like separate browser, photo, note and address programs. If you just keep all of your personal stuff in one of those, you should be fine.
@Tokyo1 , very good call on the Pasumo / Suica travel history. Here are some other tell-tales that you will want to avoid:
- search history in your Japanese-English dictionary ("Honey, why were you searching for 潮吹き?")
- kanji-henkan candidates -- your text input system will "learn" your recent and/or preferred words ("Honey, when I go to type 奈良, it autocompletes to 奈々子, who is that?")
- clipboard text -- if you copy a bit of text for purposes of looking it up, be sure to clear the clipboard later by copying some other text onto it ("Honey, why was ホテル 目黒エンペラー on the clipboard?")
- photos syncing to the cloud automatically ("Honey, why does iCloud have a picture of a wine list from Tomei?")
- smells are a BIG one! Buy some extra bars of your regular brand of soap, and carry them with you on your dates. Shower afterward and use your regular brand of soap. NEVER use the soap provided at the hotel, and NEVER fail to shower or your wife will notice the other woman's smell on your hair, etc.
- LINE uses cellphone numbers to help ensure that its users are real persons, etc., but you can have a separate LINE identity on a different device if you first create a disposable cellphone number and use that number to sign up for a new LINE account. Use apps such as TextNow, Burner and Pinger. These only generate US phone numbers, but since LINE is in the US now, it doesn't matter -- you can use the US LINE account in Japan just fine.
- If two phones would be suspicious, then get an iPad. You can do virtually everything on the iPad that you would do on a phone.
- Stow an extra shirt somewhere accessible (office, briefcase) in case you get lipstick on the first one.
- If you and your wife are not having sex, and she finds your package of condoms, then try this explanation: "Hey, since you won't have sex with me, I have to do it myself, right? Or else how could I sleep? Well, I have to do it so often that my dick gets raw and starts to bleed. Unless I use the condoms. That's why I have them. Are you satisfied?"