mono posted a spoiler comment on MakiMaki. I wasn't able to see this last night so it's not too late to post it now.
NOTE: HIGHLIGHT THE PARAGRAPH BELOW IF YOU WANT SPOILERS :D!
For preparation, Akko searching on internet for how to do H things between girls!! but as you know when you try to search with keywords "lesbian, H, ways", you will properly get to link to some porn sites, the same thing happened to Akko XD Akko help Mayu with make-up, and she learnt that Mayu has someone she love. Remember how Akko envy Mayu in last chapter? so Akko is relieved. But this time it is Mari who is jealous, as Akko get too close to Mayu (physically) Becaue of jealousness, after Mayu left, Mari hugs Akko. We will have Mari and Akko kissing again in this chapter, and they even go further....but not reli that far;)