Well in an attempt to use what little logic there is in this kind of anime, what if the Urashima male line carried in its genetics a cluster of genes that gave all the Urashima sons vast ki reserves, the unconcious ability to gather and utilise chi and subconsicious eneregy manipulation abilities (think redirecting the kinetic energy of an attack into a ki blast).
However a long time ago they realised that wielding this kind of power would only cause trouble and as such all sons have their abilities sealed from birth with a special ritul that twists their ki into a special pattern that keeps them safe (Keitaro's immortalitiy) but also ties up all that power so that they appear, to all but the most well trained eye, a bit weak and pathetic with an almost improbable ability to look on the bright side and limitless patience.
To futhur reduce the chances of the destruction of a sizable chunk of japan, the sons are taught a very defensive martial arts style, while the girls are taught the more offensive style, in this way the guys grow up kind hearted and forgiving(keitaro) while the girls grow up tough(haruka). With the hope being that with luck the girls will take care of things and the guys won't have to blow up any cities by accident.
Knowing that not all things go according to plan the weave which binds their powers can be undone with certain emotional stimulus (intense need to protect something), also when an Urashima son gets a serious girlfriend he plans to marry, or reaches the age of 25 he is then given special training after which it he can unweave the seal at will and use and train his abilities consiciously. prior to special training being received said candidate is checked pschologically to make sure he will be responsible enough with his abilities with training being postponed if the subject is found lacking.
All of this is of course kept quite by the family and the guys only find out when its time for them to be unsealed, and the girls only when it is deemed neccessary for them to know.
So when Keitaro gets smashed his body automatically steals energy from the blow to cushion his landing, before siphoning any latent chi in the enviroment to repair his body, however the slight flaw is that it prevents none of the pain just makes sure you don't die at the end of it. The Urashima elders didn't want spoilt idiots thinking they were invincible after all.
Does it hold together enough considering the appropriate anime logic?
However a long time ago they realised that wielding this kind of power would only cause trouble and as such all sons have their abilities sealed from birth with a special ritul that twists their ki into a special pattern that keeps them safe (Keitaro's immortalitiy) but also ties up all that power so that they appear, to all but the most well trained eye, a bit weak and pathetic with an almost improbable ability to look on the bright side and limitless patience.
To futhur reduce the chances of the destruction of a sizable chunk of japan, the sons are taught a very defensive martial arts style, while the girls are taught the more offensive style, in this way the guys grow up kind hearted and forgiving(keitaro) while the girls grow up tough(haruka). With the hope being that with luck the girls will take care of things and the guys won't have to blow up any cities by accident.
Knowing that not all things go according to plan the weave which binds their powers can be undone with certain emotional stimulus (intense need to protect something), also when an Urashima son gets a serious girlfriend he plans to marry, or reaches the age of 25 he is then given special training after which it he can unweave the seal at will and use and train his abilities consiciously. prior to special training being received said candidate is checked pschologically to make sure he will be responsible enough with his abilities with training being postponed if the subject is found lacking.
All of this is of course kept quite by the family and the guys only find out when its time for them to be unsealed, and the girls only when it is deemed neccessary for them to know.
So when Keitaro gets smashed his body automatically steals energy from the blow to cushion his landing, before siphoning any latent chi in the enviroment to repair his body, however the slight flaw is that it prevents none of the pain just makes sure you don't die at the end of it. The Urashima elders didn't want spoilt idiots thinking they were invincible after all.
Does it hold together enough considering the appropriate anime logic?