This is a theory I have about Akiko Minase and her infamous jam.
Note: all my information is coming from the 2006 anime adaptation of kanon.
So here is my theory Akikio minase is an Alien.
Here is why I "think" so:
So what do we know about Akiko Minase well besides her not having a husband ( or at least one that is around ) Nayuki presumably being her daughter and her general friendliness not very much.
Well there would really only be one Logical explanation. She is part of the japanese branch of the MIB. Think about it, it is never said where she works nor are we told anything about her background. Whenever she has received any kind of harm she has come out of it virtually unscathed.
- we are never shown he recover when Ayu is at the minase residence "Taking Care of her" Akiko could have easily put her to sleep and instantly regenerated.
After the Traffic Accident we only briefly see the supposed incapacitated Akiko. It could have easily been a body double
So what does this have to do with the Jam?
Well I believe her Jam comes from her! Think of her like the Slurm alien from Futurama but more Moe and with a less desirable product. Think about it the only person who seems to enjoy her jam is well herself also when humans eat it it has adverse effects on them. Besides that colour screams alien goo.
Well what about Nayuki wouldn't she be an alien to then. No! the only thing we know about the minase family situation that is definitive is the lack of a father. What if instead of just a dead beat dad situation there was some accident.
here is a situation for you:
The real Akiko minase and her husband are MIB agents. After nayuki was born her parents went out on assignment trying to save a shape-shifting alien but during the rescue something goes awry and the only one to escape is the alien and as a final favour and a cover the alien transforms into Akiko.
Things seem pretty plausible now don't they?
No!? .... yeah I did not think so.