
...vaseline is incompatible with latex condoms...

hahahahahah lmao (⌒▽⌒)
Expert!!!!

You're correct, it breaks down the latex creating holes. I think the person who gave them the "kit" was a doctor and would know this. Maybe he wants to give Hizuru a "little memento" of Youmei to keep a little longer after sex is over. LMAO Though, diarrhea and stomach cramps aren't usually considered "nice" mementos, in Hizuru's case, I'm sure they will be. LOL

Unless that's a finger cot and not a condom, which would be quite the insult to Youmei, one usually doesn't find condoms in a first aid kit. Don't get me wrong, they make a good tourniquet in a pinch, but they don't "scream" first aid. Also, vaseline isn't something one would usually find among first aid kit components, since it reacts poorly with any latex, like gloves. Medically, KY jelly is most common. It was created specifically for the medical field and has been in use by medical personnel since 1904. However, since this is fiction and the mangaka was trying to depict a situation where "necessary items" appeared out of thin air, the first aid kit was likely a better option than having Youmei ask the front desk for condoms and lube.
When I see the Vaseline and condoms
I thought (finally bout damn time). Yes! (๑•ㅂ•)و✧
I thought he's so considerate then
he kissed his tears away
...and that's when I died