<p>Couple of thoughts.
</p><p>Gai himself is only like 30, he looks older than he did at the Chunin exam in Obito's flashback, so he's at least what, 13? That's 17 years max. Since Shinobi work on a merit system and not seniority, Raiga could easily be in his late teens, early twenties there, making him anywhere between about 33 and 40 by Naruto's time. Not exactly over the hill since the Sannin are all in their fifties, and are tanks.
</p><p>Raiga was an Anbu, so he was already a powerful fighter, so it's not like all his battle power was because of one kid. Assuming he became Anbu after becoming a swordsman, bringing the prized, highly recognizable weapons of his team on covert ops, kind of defeats the purpose of them being covert.
</p><p>Next up, Ameyuri and the others are considered 'The Worst Generation' but consider this
</p><p>Previous Lot (Assuming oldest)
</p><p>Fuguki - Jinin - Kushimaru - Guy who might be Jinpachi - two unknowns - Raiga Lookalike
</p><p>'Worst Generation'
</p><p>Fuguki - Jinin - Kushimaru - Jinpachi - Zabuza - Mangetsu - Ameyuri
</p><p>'Current' generation
</p><p>Kisame - None - None - None - Zabuza - Chojuro - Raiga
</p><p>The only conflict here seems to be Raiga and his doppleganger, but we can clearly see all the same that any one iteration of this group can contain members from different generations, as with the exception of Chojuro as the absolute youngest, Mangetsu is seemingly the junior of the worst generation by quite a large margin given his little brother whom he grew up with and shared a united dream with is only like 16 himself, whilst others seemingly would long precede him and Kisame, a member of the current generation is in fact older than Zabuza, his predecessor in the group. In this respect, the "Worst Generation" might be either the ones who are considered the strongest wielders of any of the given swords, or the typically strongest generation of wielders (Eg. the seventh lot of wielders for each sword are the worst) In which respect, the turnover of each blade could have their seventh wielders having never met let alone fought together.
</p><p>While I won't deny, one would imagine "Generation" in this respect to reflect those who fought together as a group, other interpretations are possible.
</p><p>At the same time, this could just be Kishi giving props to the anime by canonizing their contribution of both the Kiba and now Raiga, without asking us to consider the entire Curry of Life Arc and simply acknowledge him as 'No longer Filler, and the need to work out the particulars weren't part of this consideration.
</p><p>Finally, for those that asked, they were called the lightning fangs, but Kiba is Japanese for Fangs, so I guess Kishi just shortened it.
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