I'm looking for manga that fit the following requirements:

-an action and/or adventure manga that contains fantasy elements; so not something like ingenuo
-female lead
-romance between the pupil and her teacher
-age gap between the two

Plus if:
-romance between the two is not evident until much later in the story
-the mentor likes someone else, but that person dies or leaves

No yaoi or yuri.

I know that my request is really specific, so I'd also like to hear suggestions that fit most of the requirements.

Ciel
Maybe... Cardcaptor Sakura? Haven't read it though.

世界のどこかに必ず
キミの居場所がある筈

Maybe 1/2 Prince?

Student-Teacher+Age gap

I think Cardcaptor Sakura fits, however the student-teacher romance happened to side characters, not the main. Still, it's a good read.

Oresama Teacher fits these request:

-female lead
-romance between the pupil and her teacher
-age gap between the two
-romance between the two is not evident until much later in the story

But it's not fantasy... 🙁

Faster than a Kiss although it's not fantasy. 🙁

I definetly second Cardcaptors. The student teacher relationship is more evident in the manga than the anime. It meets most of your requirements.

Another fantasy with an age gap(not really emphasized) is Full Moon wo Sagashite
It's a bitter-sweet love story and not added into the story until later.

Pearl Pink has an age gap but it's more about show biz.

You also might be interested in Pretear. Has the magical feature, age gap (i think), a sad part to it (not necessarily a person dying but depression 😕 )

Hope those will come to your liking! 😁

There's an old saying my late grandma taught me. When you're ten, they call you prodigy. When you're fifteen, they call you a genius. Once you hit twenty, you're just an ordinary person. About three years until I'm ordinary. Man... I can't wait to be ordinary.

H is the best student-teacher relationship manga I read so far, but it doesn't have any fantasy elements.

I double-recommend 1/2 Prince though. It has all the elements you're looking for . Thing with this manga is that the romance isn't a big part of the plot. Plus the manga is very funny...

Quote from akiranox

Another fantasy with an age gap(not really emphasized) is Full Moon wo Sagashite
It's a bitter-sweet love story and not added into the story until later.

The anime is like ten times better... I mean I don't even really LIKE the manga, but consider the anime to be one of the greats. The ending of each are especially disparate (the anime having one of the best endings ever).

It's not student/teacher though, so not really sure why the recommendation is here....