Cheapest way from Osaka to Fukuoka

Hi,

I'll be travelling to Japan soon for an university exchange and am hoping to travel to Fukuoka for a short trip (3D2N) before school begins. I'm looking for the cheapest way possible, can anyone kindly advise?

I chanced upon something known as the JR West Rail Pass - Sanyo Area but from what I understood from the website, it is not eligible for anyone staying for more than 90 days even if you're holding a foreign passport. Or am I understanding this wrongly? Is there any passes that would be applicable for my visa that can bring about savings?

If train isn't the cheapest option available, is there any way which I can contact and place a reservation for a limousine bus from Hirakata-shi (where I'll be living at) to the Airport via any online means (considering Jetstar/FlyPeach too)? Currently the only option seems to be an overseas call but I don't speak Japanese well.

Thank you in advance!

Unfortunately, it is not possible to buy the JR Sanyo Pass even if you have a student visa, because it can buy only short-term visitors.
https://www.westjr.co.jp/global/en/travel-information/pass/sanyo/

I think it's one option for what you use the LCC is to save money. If Starting point of you is Hirakata-city, then it take 90 minutes by bus or train to Kansai Airport from there. If you choose the LCC, it is necessary to check the transfer time.
Hirakatashi - Kansai Airport Bus
http://www.kate.co.jp/pc/time_table/keihan_uji_tt.html#from
Hirakatashi - Kansai Airport Train
http://www.hyperdia.com/en/cgi/en/search.html?dep_node=HIRAKATASHI&arv...

Another means is to use the night bus.
In this case, it is necessary to go by train to Umeda from Hirakata-shi.
http://willerexpress.com/st/3/en/pc/bus/route/calendar.php?off=1&hkn=3...