>>40759192
Seconding this op. There are quite literally thousands of cases identical in structure to yours. By the way, consider yourself lucky, most people have little to no coherent memories of their past lives; much less their most recent one, much less in such vivid detail, and finally much less with the memories staying with them past 5-10 years old.
My suggestion is to meditate on these memories, buddhism has some good frameworks for doing so but the gist is to just sit quietly and watch your breath and thoughts arise and disappear. Consider why you felt the need to come back, the attachment to the idea of being an American, the attachment to your girlfriend and her suicide, and your decision to suicide in your nip life. Don’t fall into the same pattern my friend, you are early 20s this life and suicided late 20s/ early thirtys in jap life, so try to build a more fulfilling and peaceful life this time around because suicide has bad kammic weight due to making your friends and family sad. Consider sending loving thoughts to your past life parents and friends and also girlfriend and forgive her for killing herself