Do I preserve these and how?

Handle as little as possible. Here are some great tips for you.

https://ourpastimes.com/preserve-paper-currency-7491165.html

http://blog.coinsupplyplanet.com/top-5-tips-to-preserve-paper-currency/

https://oldcurrencyvalues.com/currency_storage/

https://www.cointalk.com/threads/preserving-paper-money.27845/

There are containers for keeping money safe. I would seek out a "coin" collector or someone you know who collects coins and ask where they get their holders for coins, you can probably get paper money holders in the same place. Also, you can order them on Amazon at 25 for under $20. See photo for a sample of what is available.

Japanese money

Japanese Government Issued Philippine Peso. Issued by the Japanese when they occupied the Philippines during World War Two. They are in rough shape. Best to get them evaluated by a coin shop. Value about $1.00 to 10.00 each depending on condition. Coin shop does sell non acid plastic sleeves for paper currency.

I thought pesos was a Spanish or Mexican money, but the first one does say Japanese government in English. I would think Japanese money would be in the Japanese script, not English.

Yes, if the bills were printed for use in Japan, then the currency would be in Yen, not Pesos, and the lettering would have been in Japanese, not English. As William noted, these bills were printed for use in the Philippines.