Is Transit Visa needed? Haneda to Narita

I am a Filipino. I have booked my flight to the US (US resident here) from the Philippines and I just noticed that the Narita airport is quite far from the Haneda airport. I thought of just getting the limo bus to transfer airports. But upon researching, I found out that Haneda airport requires visa for people (applies for Filipinos and other nationalities) who leave the airport.
Do I need a transit visa given that my in transit stay is just for 4 hours? And I am planning to take the limo bus to transfer? I am not going anywhere else than just the two airports.

I don't know what to do. My flight's in two weeks.

You are entering Japan - you need to pass through Immigration to exit Narita Airport and transfer to Haneda Airport. I would assume that if your nationality requires a visa, then you will need to apply for one, even for such a short transfer.

Perhaps contact your local Japanese embassy for clarification.

I found out that Haneda airport requires visa for people (applies for Filipinos and other nationalities) who leave the airport.
Sounds like you got the correct information.
Delay no more, contact the Japanese consulate ASAP.

Also, the two airports are really far from each other. The bus itself takes 1h15-30 if no traffic and if you can find one at a suitable time for you. Add picking luggage, disembarkation procedures, and checking in at Narita... If you only have 4 hours between the two flights, you might not be able to make it on time to Narita.
If I were you, I'd just cancel the first flight and rebook on a flight from the Philippines directly to Narita. It might seem a waste of money especially in the case that the Philippines-HND flight was a non-refundable bargain, but it will save you a lot of money and headaches.

If your ticket is refundable, you might want to consider changing the flight. I would most definitely avoid this kind of connecting. Delayed departure/arrival, long queue at immigration, picking up your luggage and get to the bus, and traffic condition between narita and haneda. Any or some of these can screw you up from catching your connecting flight.

btw did you purchase the most cheapest flight you found online?

Jetstar Japan, Philippine Airlines have direct flight to Haneda from Manila. The former could be cheaper. If I were you, I would not hesitate to cancel the Narita one.

Add up that it's probably 90 minutes between airports and 60-90 minutes to clear immigration, and needing to check in and get through security at Narita, and I don't know if you can do it in 4 hours. If everything goes perfect, you just might squeeze in.

Rebooking for a flight in and out of same airport may be a lot easier than getting a visa in 2 weeks anyway.

You can apply for a transit visa upon arrival at narita. This will allow you to get thru immigration, collect your luggagea nd get into a bus to take you to haneda. There is a bus leaving every 15mins and bus trip takes about 90mins w/out traffic. This will work assuming no delays in flight arrival to narita and the bus trip to handeda. Getting the transit visa takes about 5 mins assuming no long line.