Perhaps they choose a honeymoon destination that is known for its dangerous magical creatures. They end up having to team up with the local mages to fend off these creatures and in the process, they learn more about each other's strengths and weaknesses. Also, it could be interesting if they stumble upon a prophecy during their honeymoon that involves their future together and the future of Fairy Tail as a whole.
One idea could be that the main couple from Fairy Tail goes on a honeymoon to a magical island. There, they discover a hidden ancient magic that they have to protect from villains who also find out about it. Another plot could involve them facing relationship challenges during the honeymoon, like misunderstandings due to magic gone wrong. For example, a spell makes one of them forget parts of their relationship, and they have to work through it to rekindle their love.
A possible plot is that they go on a honeymoon in a parallel world where Fairy Tail doesn't exist. They have to rely solely on each other and their love to survive in this strange new place. They might meet alternate versions of their friends or enemies, which would add an exciting twist to the story.
The best chapter pointer here is Chapter 117, "What Jiang Li Can Do, She Can Do Too!". It opens with Fragrant and cloyingly sweet potatoes and corn were out of the pot, and Qi... and closes on Since entering puberty, his mother had exerted strict control over his....
The best chapter pointer here is Chapter 164, "Congratulations to Jiang Yan for scoring one point!". It opens with Damn, the production team is so shady, they're still doing a live... and closes on The current Jiang Li did indeed make him see her in a new light, to some....
Look to Chapter 168 for the clearest answer. It begins with Su Yinwan spoke those words with a pitiable expression, then lowered her..., keeps building through The next second, a crisp notification sound rang in her Divine Sense,..., and lands on The Gu Family had strict family education;
The best chapter pointer here is Chapter 144, "She's Too Bullying!!!". It opens with Ordinary people would have been at a loss in this situation by now. and closes on He then noticed the hand—fair and slender, not at all like an auntie's..
The best chapter pointer here is Chapter 129, "Spent Millions Only to Drive Traffic to Jiang Li?!". It opens with When they saw that the live chat was full of praise for Jiang Li, those... and closes on With that thought, he smugly turned on his phone..
A practical answer is Chapter 139, because it turns the idea into a concrete scene. The chapter opens with Wen Jiaojiao's live stream was inundated with a wave of question marks., adds pressure through How was this plot supposed to crash and burn now?, and ends on The audience in the live stream.
Chapter 138 is the strongest chapter-level answer because it starts from Is there such a good deal? and follows through on Could it be that the poison also had a side effect of making a person more....
Look to Chapter 140 for the clearest answer. It begins with In the evening, the setting sun was like blood, dyeing the entire earth a..., keeps building through Although there had been a cool breeze in the mountains in the afternoon,..., and lands on I was just joking, just joking." Seeing that.
Look to Chapter 170 for the clearest answer. It begins with Watching the two who had long remained silent, the PD shifted his position..., keeps building through If you don't set off soon, you'll probably miss lunch." Hearing this, Su..., and lands on [Didn't the other guests also do farm work in.
Look to Chapter 128 for the clearest answer. It begins with Still hungover, Huo Ziyang had just awakened from a blurry dream when his..., keeps building through He clicked his tongue in annoyance and picked up the phone., and lands on There had been no shortage of Weibo posts criticizing Jiang Li.