This is a story of a 10 year old kid, summoned and imprisoned, he escapes and has his revenge upon which his companions decide to "betray" him and send him back home. The problem is that it's done very poorly for example:
1. Why do they need to betray him? they could try to make him go back.
2. If they wanted him to go back, why didn't they just give him a reason to, instead of befriend/seduce him? Do some groundwork before the final fight so he prefers that option.
3. Why does he return 10 years later? There's no real reason, he was, put simply, rejected, both by his friends and girl. Also, he spent 6 years in that world and 21 in his own reality.
4. He's mostly a reasonable guy, but on this point the character makes no sense. He says he's back for revenge, but is he to destroy all the 6 kingdoms to get it? for being rejected and sent home? isn't that a bit overkill? Not to mention the collateral damage the unrelated civilians would suffer for his damaged ego.

At least it all happens quick, so in 1ch it's done. Leaving that aside, it's a pretty standard summon story plus revenge, so far, it's not a particularly good story but it's not terrible either. There are also some other things that I won't spoil, it's a bit confusing with al the magic and outer magic, but the MC's trying to figure it out, so I guess it will make sense eventually.
As for the character, he's rather inconsistent and as said, I don't get his motives, his companions seem to accept his explanation like a logical one too, so none of them question him on what his intentions are and how far he's willing to go. The FL on the other hand is interesting, she looks slow and oblivious but she always surprises the MC. The ain't much to say about the rest and the antagonists have had little "screen-time" too.

Overall, it's a decent read if one can look past a very lousy start, it being short is good but the lack of meaning persists, maybe the author will address it later, it's only been 20ch.