There is a sequel to this particular story... It's called "Ichido dake no uta". You can do...

I just checked : Doujinshi --> Originals --> Mori no Keo series --> Ichido dake no uta.
If they ask for a password, it is given in the link that I gave, right under the link for downloading Naono Bohra sensei's work.

its also on mangago...
http://www.mangago.me/read-manga/itsuwari_no_mori/

I don't think it's the same ? The sequel I was talking about involved this very couple, the gun-dealer and Zai, it's around the same number of pages, and if I remember correctly, in the sequel, the "master" want a new body-guard in order for Zai to be unarmed... I don't think this chapter is included in Itsuwari no mori. But I may be wrong !

Sorry, I meant to like this, not give thumbs down.

oh, sorry my bad. its not the same. the one i mentioned has like 4 stories about monsters and their masters in one. i dont remember seeing Zai or the Merchant unfortunetly :(

you almost made me cry, i was soo happy i cant believe they actually had a sequel this whole time, this is my favorite oni pair <3

You probably already know, but it's on mangago now ! http://www.mangago.me/read-manga/ichido_dake_no_uta/
And there's even the Vim/Valcan sequel : http://www.mangago.me/read-manga/mori_no_koe_dj_nettai_no_mori/

ahaha actually no i didnt realize they were on here at all #－.－)
Thanks for telling me.. I should pay better attention considering how much I love this mangaka

Héhé, I know right ! She's the best ! (๑•ㅂ•)و✧