One of many of this type of signs posted in Japanese subways and train stations. Click this smaller version to see one large enough to read (it's in both English and Japanese).
March 20, 1995 was a Monday and I had a doctor's appointment in the early morning. Being a teacher, I was on a schedule that was skewed toward a late start and finish so I wasn't happy about this but I needed to go to a clinic in the Hiro-o area for follow-up on a case of Bell's Palsy I was recovering from. I had neither the option to change the time nor skip the appointment since I'd been on steroids for over a month and they had been driving me (literally) crazy. Since my face was no longer partially paralyzed, I desperately wanted the doctor to tell me I could stop taking the medication.
On most Mondays, both my husband and I had a day off, slept in, and rarely went out on trips around Tokyo. It was extremely rare for us to be out at all, let alone early enough to be catching a train during rush hour because we preferred to rest on the second day of our "weekend" (Sunday and Monday were our days off). The combination of mood-altering steroids, getting up abnormally early, and having to see a doctor (which I passionately hate) had me more than normally irritated, but my husband was dawdling and we weren't getting out the door as early as I wanted. We left about 10 or 15 minutes later than I wanted but finally made it to the subway and had to change our travel plans and switch to the JR line rather than switch over to the Hibiya line. When we reached the transfer point at Ebisu, the trains were stopped and the station was packed with people.
My husband and I waited awhile to see if the trains were going to get up and running again. Announcements for stopped trains are notoriously vague for various types of accidents but we assumed that there may have been a jumper who committed suicide on the tracks. Since I was antsy about missing my appointment because I believe you have to pay if you miss one (and the clinic is very expensive and not covered by insurance), we decided to leave the station and try and catch a cab. It turned out that there were so many stranded people that there wasn't a cab to be found. In the end, we walked from Ebisu station to the clinic in Hiro-o. We called the clinic to let them know we were unavoidably stuck.
When we reached the clinic, the people there were very understanding because they'd already heard that something big was going on and several subway lines were stopped. While the doctor checked me out, my husband walked to a bank machine to get money to pay what we were sure was a big bill. He saw a television monitor along the way and noticed there was some serious problem going on with the subway. People were lying around on the ground and it had all the appearance of a major accident.
It wasn't until later that we learned that there had been a domestic terrorist attack in Tokyo. A religious cult, Aum Shinrikyo, had distributed sarin liquid gas in subway carriages on three lines bound for the direction we were headed. Based on the general times we were told the gas attacks were initiated, we were about 10-15 minutes behind the affected trains and planning to board two of the three lines (Marunouchi and Hibiya). If my husband hadn't caused us to run late and if we had acted on my anal-retentive need to be early all the time, there's a pretty good chance we would have been right in the thick of it. Since that time, I've not gotten seriously upset at my husband for not wanting to leave extra early to accommodate me.
Prior to this attack, Aum Shinrikyo was mainly known for stationing recruiters, some of whom were dressed in cute animal costumes, at stations. My husband and I used to see them fairly regularly at our local JR station and laughed at how silly the big blue animal costumes were and how odd it was as a means of trying to snag people for a religion. No one really gave them much thought outside of those who were a part of the cult until the attack. After the attack, posters of the perpetrators who got away appeared all over Japan and the cult's leader, Shoko Asahara, was arrested and is currently awaiting execution. Everyone knows who they are now though the group has changed its name to Aleph to try and distance themselves from the cult's violent episode in history.
While the wanted posters were up, the attack was fresh in everyone's minds but few people think much about it this days except as a footnote in history. Terrorism is still something that foreigners do, mainly to each other in the minds of the Japanese. They don't seem to think much about the fact that the only terrorist act committed against Japan was an internal affair.
The main lingering legacy of the gas attack is the posting of the sorts of signs at the top of this post. The line that says "if you spot a suspicious object, please notify the staff" was added after the attacks to encourage people to be wary of they type of devices used to distribute gas amongst the subways in the attack. Since the attacks were carried out by people who left plastic bags full of liquid sarin which were wrapped in newspaper then punctured with an umbrella tip, even mundane items are to be viewed with suspicion. Prior to this incident, people left newspapers and magazines on the trains and other people would read them. Since the attack, special bins have been placed in major stations to leave only magazines or papers in so that they can be read by others. Such items are no longer viewed mainly as an innocent act of anonymous sharing when left on trains and signs discourage people from leaving anything behind though careless people do it anyway and those who don't remember the details of the attack.