I think I was able to put an a few pieces together right now, and seeing that theres no ot...

I think I was able to put an a few pieces together right now, and seeing that theres no other explanation on here, here's my crude analysis of this (skip to the end for my interpretation of the ending):

Im going to start at the last chapter for the main story (ch6). I don't know if everyone figured this out already, but this chapter shows the events that happened BEFORE the first chapter. Taisei is pretty well off, since he has a job and partners and all. But after a few pages, we see that he's dissatisfied with his life. We see that he goes back home to see kouta (who says "taisei" when he sees him), and that is the same scene in the beginning of the story.

In the last (prologue) chapter, when taisei said he'd always hated "these white hands of mine". I'm considering the idea that taisei had an inferiority complex to kouta, which was a reason why he never got into the family business and instead went away to work.

On mangaupdates, one of the tags this manga was listed with was "unexpressed feeling/s" and i believe that in the past, taisei was confused about his feelings for kouta, so he kissed him brother and then left his brother, who was completely confused. And later on, he regrets it, which is why he returns home, because he "wants to ascertain those feelings".

There were a lot of comparisons with indigo throughout the manga. Taisei said he was "not going to stain (kouta)" with his feelings. Taisei's feelings for kouta were also compared to the short lifespan of indigo at the end of ch4, and he is probably insecure about his relationship with/love for kouta, and cant express them to him? Not to mention he is still confused about them. In ch2, he says "the day may never come when i can put (these feelings) into words". Well, they say that their relationship was "neither brothers nor strangers". But maybe it's something that can't be defined with a label, cheesy as it sounds.

A major theme i noticed in this manga is "family". Kout is really hurt when taisei says he never thought of him as a brother. I dont think he felt that he belonged in taisei's household. And taisei's family kept mentioning, "what connects us is not our blood, but the deep indigo stain". They accept kouta as a part of the family. But kouta is still uncertain, which is why he leaves.

On the first chapter, taisei wonders if it's too late to become an artisan. Maybe he really was dissatisfied in his previous job, and now he wants to go back to his roots? Or maybe he is trying to reconnect with kouta? In the end, we see that he has gotten a job(?), teaching children how to dye. I can't see his fingernails, but i can almost bet theyre stained with indigo. Maybe it symbolizes how he and kouta are connected.

In the end, kouta came back. Taisei knew this would happen, and was patient enough to wait. Perhaps he knew kouta had to figure his feelings out? Before, kouta says, "taisei...there's something i never told you" (he later says it was that he was thankful taisei held his hand during his father's funeral), and after, taisei says, "kouta, there are words i want to say to you." I'm thinking that this is a sign that their relationship is slowly beginning to develop, but they just havent spoken the words that they want to say to each other yet. Again, it's "unexpressed feeling/s" and taisei says "the day may never come when i can put (these feelings) into words". But i think they just need a little time and communication, and that this is the beginning of a love story, and it leaves how it plays out to your imagination. But i do think that they will very likely work out.

I mean, there's still a chance that the mangaka completely BSed this story, but I believe art conveys something, even if unconsciously. Thanks for reading! I probably veered off a but as I was typing this, haha. Took too much brain juice...but I'll see if I reread this in the future and understand it better :)