Have I missed my chance to finish Rikia's tattoo?
Right after defeating Kanda, you get a chance to wander around Kamurocho with Rikia.
While you show him around the town, it is hinted that you should probably take him to a specific tattooist located off a back alley in Pink street, so that he may get the viper tattoo on his back finished.
However, I simply ended up going with Rikia to wherever he wanted to go and didn't make the detour. You eventually go your separate ways, though apparently Rikia will meet up with you again later.
My question is, have I missed my chance to take Rikia to the tattooist, or will I have another opportunity?
Solution 1:
After playing some more, it turns out that you do get another chance to finish Rikia's tattoo.
After defeating Kanda, your next plot-line goal is to return to New Serena and update Date. Once you get there, Rikia shows up and you have another chance of wandering around town with him before advancing the plot. One of the things you can do while showing him around town is getting his tattoo finished.