I had an idea for an isekai manga/webcomic I want to make in the near future.

Okay, so it starts off on the 16th birthday of the MC, Takeo Shirogane, an athletic high school student living in Kyoto, Japan. Among the birthday presents he gets at the little family party is, from his mother, what appears to be a ring and a pendant that she received from her former lover, who just so happens to also be Takeo's real dad. The conversation ends up segueing into how he, Takeo's father, claimed to be a prince from another world and that when he needed to return for some "royal errands", the two would always depart at the mouth of a cave at the beach. (Also, Takeo's heard this story before.)

Super early next morning (like, 4 in the morning), Takeo decides to get up and walk down to that very beach, ring and pendant in hand, and go into that cave his mother spoke of to just maybe find out his father's whereabouts. The pendant ends up reacting to the magic circle inscribed on the wall inside that cave, causing it to magically open up a secret passageway, a passageway that just so happens to lead to the other world. And so the journey to find out the truth begins.

Was going to give it a kinda shonen manga vibe, no harem (probably a party of 3 guys, 3 girls), MC isn't stupidly OP, and more to the actual story than just wish fulfillment. Lots of occasional references to jRPGs (especially FF6 and FF7) and other isekai.