Sorry, I'm not very familiar with the specific 'ulala session love fiction' song lyrics. You can try to search for it on music platforms where you might find detailed lyrics explanations.
You could also check on social media platforms. There might be fan pages or groups dedicated to 'ulala session' where fans share and discuss things related to the band, including the lyrics of 'love fiction'. Additionally, YouTube music videos of the song may have the lyrics in the description or as captions, which can be a convenient way to access them.
I'm not sure who Aku specifically is. Aku could be a person with a great imagination who tells all kinds of stories, like adventure stories, fairy tales or even true - life stories.
It could be someone from the Naruto universe who doesn't like Naruto's newfound fascination with Aku. For example, Danzo might see Naruto's interest in Aku as a threat to the stability of the village and try to stop Naruto from further exploring Aku - related things. So, Danzo could be the main antagonist in this case.
The character of Aku could be developed in a 'pregnant Aku in Samurai Jack fanfiction' by exploring how he interacts with the world around him differently. He may become more reclusive as he doesn't want others to see his 'weak' state. Or he could become more aggressive in trying to protect his pregnancy, which would be a new aspect of his character. Also, his relationship with his own power might change. Maybe he has to find new ways to use his magic that don't harm the unborn, which would force him to grow and adapt in ways he hasn't before.
One idea could be a crossover where Aku accidentally opens a portal to the Naruto universe. Naruto, being the curious and brave ninja he is, decides to explore Aku's world. They could start off as enemies, but gradually come to understand each other's motives and end up teaming up against a greater evil that threatens both of their worlds.
I'm not sure who specifically wrote the lyrics for a song titled 'lirik never ending story'. It could be written by the songwriter associated with a particular musical version of 'The Never Ending Story'.