>Make out
>"Hm, there was another girl at the mansion, I think... she sounds really dangerous, but the others didn't want her to fight. Do you know about her?"
How comfortable are we with getting a ghost from the graveyard, at this point? I wouldn't have felt too guilty about trapping one of those aggressive ones from the abandoned house, but if most of them are still benign and sentient...
Would it be completely insane to ask Youmu if some of the spirits would be willing to hang out in occupied homes during the summer to help keep things cool? Not forced, but requested? Some ghosts might want to get out some. That'd probably interfere with things too much for her to consider it, but it'd be an easy solution to the actual heat problem.
---
And yeah, agreeing that openly and directly helping Renko would be a little much as long as the SDM is being reasonable. If they try to enslave Renko, threaten her with Flandre-kyuuing, try to kidnap Mary for emotional blackmail, or something else stupid like that, THEN we're justified, but as it stands we do owe it to them not to completely stab them in the back.
I didn't mention it, but I personally consider Mary's observation role to include keeping an eye on Renko - if she goes off the deep end like Utsuho, then we're best qualified to gently bring her back into line.
---
Also, am I remembering wrong, or did Sakuya basically threaten to kill us if we told anyone how her ability works?