I think he means stealing the tank, as in she just does it without thinking rather than deliberately.
Although it doesn't really work without the か at the end, there's also the possibility of him going "You are doing this on purpose, aren't you.", which either implies that he thinks she cried and guilt-tripped him on purpose, or that he thinks she's returning the tank right in front of him now just to make him feel guiltier.
Although it doesn't really work without the か at the end, there's also the possibility of him going "You are doing this on purpose, aren't you.", which either implies that he thinks she cried and guilt-tripped him on purpose, or that he thinks she's returning the tank right in front of him now just to make him feel guiltier.
That's possible too.
Hnnng...
Sniffle...
Gloooom
I—I was not!
Sneeeak
To get mad without hearing her side...I'm a failure as a kindergarten principal...
Hold it, Mika-chan! You were trying to steal something again, weren't you?
Mikgha didn'd do anythigg wrong...!!
I was just trying to put it back after it fell down!
Beeeam
Hig'k...
I'll give you some salmiakki, so don't cry!
G'nnngh
Eh!?
Ah!
Ulp
Er...don't tell me you are doing it on purpose?
Ah...! I-I'm sorry, okay! Teacher made a mistake...!