[Sangetsu]

If you visited before and checked "no" on your card, and were not denied entry, then doing so again will do less harm than checking "yes". Checking "yes" now would mean that you checked the wrong box when you entered in 2014, which would be a bigger problem than clicking "no" now.

The embassy will not be able to give you an answer because bureaucrats in Japan are always afraid of giving the wrong one.

Technically-speaking (and I say this as a former police officer), the word "convicted" is somewhat different than "pled no contest to", which is usually the case with minor misdemeanors. You could check "no" on the box, and in the very unlikely event you were called out, you can state that you were not actually convicted, but "pled no contest", or assumed responsibility for the offense.

I would not lose sleep about the problem. Unless the charge is related to drugs, domestic violence, or a DUI, they are not going to prevent your entering. And in the case of a DUI, Japan will not deny you entry, though other countries (like Canada) will not let you in.

It has been 5 years since your offense, if you have kept your nose clean, you should be trying to get the offense expunged from your record. An internet search should be able to point out an attorney who can do this for you. it is worth whatever time and expense is involved. Once that is done, the record no longer exists, and you can honestly and legally check "no" in the box. Someone I know was able to get a felony manslaughter conviction removed from his record 10 years after he was released from jail, getting a petit theft charge removed should be easy enough.