Oh hey, that reminds me of a story I thought of ages ago for Destination Unknown, which then expanded to the entire After Eden album
Basically, DU was the song for the final battle, with Hikaru aka Hero vs. Keiko Evil Overlord in order to save the Damsel in Distress Wakana - so throughout hikaru's lines are like the hero's "I shall defeat you and save my home town!" Or "hand back me darling!" Or "you killed my father" etc. Etc. Meanwhile, keiko's verses represent the Evil Overlords snarky comebacks "You'll never defeat me!" "Haha wakachan is mine" "No, I AM your father!" Etc. Etc. Wakana's high-pitched kajiurago 'eeeeestomiyyaaaa' in the background is the damsel periodically calling for the hero's help
As for the rest...(Not in strict album order)
Eden: happy 'valley' song, I.e. The one that plays in the valley of peace or whatever when Hii-ro (haha see what I did there) is still a simple farmboy living with his family amongst meadows of flowers and birds etc.
Magia: evil keikolord sweeps in with minion army
Sandpiper: sad song of hii-ro lamentiing dead and pillaged hometown
Mune no yukue: hii-ro goes on epic journey to the great city to seek training in order to avenge family + village, meets obligatory old mentor figure who agrees to train him (played by double-up keiko)
Kotonoha + kugatsu + snow falling: obligatory 'reflective' songs that play during hii-ro's angst monologues to him/herself as he/she remembers past
Magnolia: female assassin theme song - the female assassin being wakanadamsel
In your eyes: hii-ro + wakanadamsel falling-in-love with helpful input from keikomentor (that explains keiko's lines in the song)
Destination unknown: after wakanadamsel gets kidnapped by evil keikolord, and keikomentor obligatorily dies (during which kotonoha/kugatsu and/or snow falling can be inserted depending on whichever is appropriate), epic final battle occurs for hii-ro to avenge family+village and save wakana damsel
Symphonia: song of triumph, keikomentor miraculously alive again (something like 'I faked my death to make you stronger' or along the lines of that), village is rebuilt, hii-ro plus wakanadamsel married with blessing of keikomentor, and in the final scene they all sing happily and frolic in the meadows of the peaceful valley
I'm sure I forgot a song or two because there are 13 songs in the album but I only put 11 here but I forget which they were and I'm on my mobile and cbb looking it up...