Mc (male) is a low rank adventurer despite being useful to the guild thanks to his witness. Accidentally stumbled on a powerful dragon in a labyrinth and died. Or so he though but woke up as a skeleton and decided to use that to his advantage toward his dream.
Super interesting plot! Getting better the more you read! Quite mature story with nice character psychological development aspect.
Not harem! Going toward Op Mc...
Nozomanu Fushi no Boukensha