Mrs. Yamada gave me a spare key to her apartment the same week I moved in next door, pressing it into my palm before I had even finished introducing myself. "Just in case," she said, waving off my confused thanks, "otherwise, what's the point of having a neighbor at all?"
I dropped the key into a kitchen drawer and, if I am honest, forgot about it almost entirely for the next four years. We waved at each other in the hallway, occasionally shared vegetables from her small balcony garden, and lived the comfortable, mostly separate lives of neighbors in a busy building.
Then, one ordinary Tuesday, I noticed her newspaper had piled up outside her door for two straight days, something that had never happened before in all the years I had known her. I knocked. No answer. I called her number, listed on a card she had given me alongside the key. No answer there either.
As luck would have it, I happened to be working from home that particular week instead of traveling for work, the way I usually was on weekdays. I found the spare key exactly where I had left it years earlier, let myself in, and found her on the kitchen floor, having fallen the previous evening, unable to reach her phone.
The ambulance arrived in no time once I called, and she recovered fully within a few weeks, though she likes to remind me, only half-joking, that she gave me that key for exactly this reason and had simply been waiting four years for me to finally prove useful. I have kept a spare key of my own ready for her ever since, tucked in the same drawer, no longer forgotten.