KZbin seems to hate when I go into details regarding this show its annoying .... About Yuuki .... first of all we know ... Rimuru suspects ... while he is reasonably sure he has no proof... he also does not know why and if it is of yukis free will ... Sudenly acting differently towards Yuuki would tip his hand and make Yuuki aware that he suspects him ... so its better to behave as before and play this close to the chest ... Same for Yuuki ... with how Rimuru is Yuuki probably suspects Rimuru is suspicious of him but has no proof ... and changing his attitude suddenly would just make it obvious ... In addition Yuuki has a public face he needs to keep going as the Benevolent and Freespirited Guildmaster ... as he does not want to lose his position at this time ... so Yuuki needst to also act the same as before .... As such they just dance around each other .... In addition Rimuru does not want to see Yuuki as an enemy for multiple reasons ... if possible he would much rather just get along with him like this ... In addition the children are still officially under Yuukis custody ... getting cagey with Yuuki would put them in a precarious position if not danger ... So Rimuru has ample reasons to keep the status quo with Yuuki The Wastelands are not Darguls domain per see but his domain is located there .... as for the origin of the wasteland? Milim .... or more precisely the 7day 7night slug fest between Guy and a Rampaging Milim .... that ended with Ramiris intervention .... the place where the First Generation of Demon Lords was formed ..... Kagali being Kazalim ... she knows about the Ruins in Claymans domain ... as it was here home base before that ... thats what a lot of her reaction were about ... Kagali has emotional attachment to that place ... for spoiler reasons .... Tiss sensei is an invention of the Manga ... she is not from the novel instead the Teacher in this moment is an ex A-ran called Klaus ... and she does not go with them in the manga to Tempest ... its an interesting divergence for the anime ... I understand why they made it as Tiss is more involved in the anime with he ovas and such ... but it makes some of the things that happen later a bit strange ... since she is there , there is no need for someone to watch over the children ... something that comes up during the festival ...