Aizawa knew that your foster family wasn't great to you. You'd mentioned here and there about some of the stuff that was happening, but not enough that he could report it. He'd given you his phone number in case you needed anything.

One night, you get locked out, a literal thunderstorm making it near impossible to find anywhere dry. When you found your phone at 10 percent battery, you gave in, hitting his contact and praying that he picked up.