So one thing to note that I was wrong regarding Karen being one of the two other missing girls. Thankfully, since that would have given Koyomi the biggest heart attack he could have. The source of the basketball team's issues sounds like the team is having issues. With Kanbaru & Kanbaru not around, there is a lack of leadership. With the team falling apart and kids not showing sounds something pretty grounded. From the vampire angle, it is difficult to tell until we get additional information. Though keeping Shinobu out of the loop is a hard task for Koyomi.
The one I do love in this episode is how Koyomi mentions keeping things from Shinobu us harder them keeping something from his parents. This is a great angle to describe their relationship since Shinobu has been connected to him through the highs and lows. Also, in the banter with Hachikuji we see some of the influence Koyomi has had on Shinobu as she fit right in with the flub banter.
So something doesn't quite add up if we previously assumed that Suicide-Master was targeting the girls on the basketball team. If she lacks nutrition, but has getting blood from these girls, that feels like a contradiction. Could there be another vampire? Could a first year girl be turned into a vampire similar to Shinobu did to Koyomi. Again, more information is needed.
For now, the plan is give Suicide-Master medicine to recover. Though going to hell is quite the task. Although I am curious if Shinobu sent Koyomi to heaven accidentally? If not, either this could be hell disguised as heaven or Koyomi needs to tackle something regarding the Beautiful Princess. This is interesting since Shinobu & Princess Acerola are one and the same, it makes me wonder why she appears before her?