I emailed the Japanese embassy here and got a very vague response.
CCfed JNTO and they replied with:
As of the moment, we have not received clear guidelines for the Philippines
for entry following the changes on October 11, though it is our opinion that
it would be better to err on the side of caution.
If we are to follow current regulations about the RT-PCR test requirement,
it depends on the age of the children:
- If they are below 6 years old, they are NOT required to take an RT-PCR
test PROVIDED that the parents and/or caregivers have negative test results
(regardless of vaccination status).
- If they are 6 years old and above, they are required to undergo RT-PCR
testing if they do not have a valid vaccination certificate.
A valid vaccination certificate must fulfill the following conditions
specified by Japan's Ministry of Health, Labor and Welfare:
https://www.mhlw.go.jp/stf/covid-19/border_vaccine.htmlMore information about the RT-PCR testing here (Question 11 in the FAQ
relates to RT-PCR testing for minors):
https://www.mhlw.go.jp/stf/covid-19/border_test.htmlRegarding the multiple entry visa, JNTO does not have oversight on visas as
the Embassy of Japan in the Philippines handles all visa matters. They will
provide updates when they decide on how to handle the visas as mentioned in
their website:
https://www.ph.emb-japan.go.jp/itpr_en/00_000035.html Please monitor the Embassy's website for any changes. Should you need
assistance on anything visa-related, the Embassy has a list of accredited
agencies that may assist you:
https://www.ph.emb-japan.go.jp/itpr_ja/00_000253.htmlWe hope the information above helps. Please also check JNTO's website about
traveling to Japan for more information here:
https://www.japan.travel/en/practical-coronavirus-information/