Often useful in these cases to search for availability for each leg separately. It seems like there are some available options for KUL-NRT.
For the return one way on MH (business class) on Aug 30 DPS-KUL is 190 GBP. There are Avios seats available in Premium Economy on JAL on the Aug 31st (40000 Avios + 30GBP). On Sep 1st seats are Avios available on MH (business) and JAL (all classes) for KUL-NRT.