...especially when the character says it so positively.
Megumi's Diary is not the kind of series where such a statement presages disaster, explosions, fire, alien invasion, or what-have-you.
Megumi's plan is pretty simple: she and Jun will go to school early the next morning in order to apologize to their teacher; there is no opportunity for a spectacular failure. All that happens is that they learn that their teacher came in even earlier, left a note for the Principal, and left; and now doesn't answer her home phone.
For a teacher--especially one with Matsuda's reputation--to be so thoroughly hurt by a student's offhand remark, there must be something else going on...and I suppose I'll mention it here as soon as I've figured out what the hell it is.
I have rejected any notion of Matsuda being in love with Jun, though. That's just a non-starter; it doesn't fit the kind of story I'm trying to tell--and besides, I've already got a (former) transvestite in the story. A cross-generational lesbian romance is beyond the scope of this project.
Matsuda, I think, is at a crossroads in her career as a teacher. She's in her late 20s and unmarried, which is a bad place for a Japanese woman to be, even now. Although fewer women than ever are getting married in Japanese society, the women still have biological clocks, and their society still tells them that a woman over 25 who is unmarried will probably never get married. Her instincts are clamoring for attention and she can do little about them.
Jun's comment cuts to the quick because Matsuda is already unhappy with her life; perhaps feeling that she has sacrificed much in order to teach, the lack of respect she perceives from some of her students has finally gotten through whatever emotional armor she once had.
This makes sense to me; and I think Jun's reaction to this is pretty realistic: "I was just blowing off steam, damn it!" Despite her guilt at making her teacher cry, she's going to continue to be defensive about the situation; but it'll be Jun who--learning that their teacher seems to have just left her life--worries that Matsuda-sensei is planning suicide. She will convince Megumi to cut school with her, and they'll go first to Matsuda-sensei's apartment....
Well, I'll say this: Matsuda-sensei is not planning suicide. I'm not sure what she is doing--drinking, or playing video games, or something else--but it's not suicide. I've given some thought to it being something she might find embarassing, but I have no idea what that might be. I would like it to be relatively innocuous; the series is supposed to be lighthearted.
--I say "lighthearted" even though there is an approximate bucket of tears expended in chapter two's 26 (so far) pages--
But in the spirit of "school life" stories, all I can say is, "THIS IS YOUTH! LET'S ALL RUN TOWARDS THE SUNSET!"
...no, that doesn't make any sense to me, either. But it's what happens in these kinds of stories, sometimes.