I did not check whether or not anime girls wearing cardboard boxes is a thing. If I was a betting man (knowing what I know about anime and the Internet), I would say it already is. If there isn’t, then I have a brilliant idea for a new anime series:
An otaku who is obsessed with collecting cardboard boxes leaves his house one morning while carrying a large stack of boxes. While crossing the road, he is accidentally struck by a fast moving box truck (see what I did there), killed and then reincarnated in another world. In this fantastical world, he discovers all of its inhabitants have never known the wonders of cardboard boxes. At this moment, the otaku uses his vast knowledge of boxes to start a "big box" store which caters to all your storage needs.
One night, while working in the store, an attractive female comes inside clothed in nothing but her undergarments. She explains that her clothes were stolen, but were actually lost due to her poor gambling habits. He offers her one of his cardboard boxes to wear as a temporary solution. After putting it on, she graciously thanks him and heads home.
On her way home, numerous other women see her unique clothing choices and become captivated by the exotic fashion choice of her attire. The very next day, the otaku’s store is flooded with women clamouring for cardboard boxes to wear. One thing leads to another and this otaku goes from running a simple storage supply store to becoming the number one fashion designer in all the kingdom, who just happens to use cardboard boxes as his preferred medium of choice.
That’s my idea. I'm not going to lie, if this was actually a real anime series, I would watch it. And if anyone from an anime studio is reading this: いつでも電話してね.