You're assuming that 1) the dream wasn't magically induced by Iris or even the guardian (we don't know if it has or hasn't been yet).
Fair point. Let's see how this plays out then.
2) Iris has always been trying to be dominate, but the MC would run and tell his mom and his mom was obvious strict/but fair to both of them. In the past Iris could never have gotten away with this stuff. Your choices recently are more perverse/different than the past, this is the first time you're doing this stuff, also the MC is still feeling shame at this point so its not like he can run to his mother like usual. Since hes just as guilty and his mom is taking these punishments more seriously. There is hints Iris was always bossy/domineering in the past, but not like this.
edit: too lazy to change it, mom=guardian every time
Hmm... but it doesn't seem very realistic to me that (a) the MC suddenly has the idea of stealing mom... er, guardian's panties (maybe he's wanted to do that for a while, but I'd imagine he wouldn't decide on a whim like this; it's more the kind of thing that might happen if both ... er, guardian and Iris weren't at home and he had a couple of hours to build up his interest... or if he had been thinking about doing this for a while (it would be nice to drop hints here and there that he had been thinking about doing this before). In other words, a number of pervy choices are made by the MC in the course of a single day; it would seem more natural if they were more spaced.
(b) Iris also suddenly deploys domineering behavior (not simply bossy) of a rather high level -- foot kissing and licking, ass licking, shoving something up MC's ass, helping... er, guardian with punishing (and mocking his small penis while doing so). Even if she was bossy before, say about making the MC do more chores than her, or insulting him (I liked that her first line was "Hey, stupid!"), this is quite a leap forward. It would be nice if we could see that some lighter things ("carry my books", "do my homework", "it's my turn to wash the dishes but you'll do it because I say so!"), perhaps even a little kiss on the shoe here and there, had already happened before. (Maybe the MC could remember such behavior, how he complained to er, guardian, and how she was kinda fair to him and protected him while at the same time suggesting Iris was not doing anything bad -- she said once the MC should show "proper respect" for Iris; it would be nice to deploy this now and then to show that er, guardian does think MC should be more submissive to Iris).
Now, we all want to get to the good stuff as quickly as possible, and I think it's OK if you're not so much into making MC's descent to his natural place in this society have too many steps. I'm just offering comments, in case you think you can use any of them.