Man this one made me think XD Though after thinking about how one can become victorious in comparison to another I came up with a lot >_>, like: becoming successful, or they succeeded in a dream that both shared or achieved a different social status/something great. so hopefully one of those is what you meant........in terms of the whole bishie thing, characters in manga are usually prettier or not true to real life so I'll let you be the judge if you do or don't like the manga style.
Magi-
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Has one arc where it deals with one of the main characters and his childhood friends' reunion, the main character had been in poverty but lifted out to be a prince when his father the king found out about him. Then later the main character still has success, despite not being a prince anymore so that whole relationship and arc was based around the sort of thing you're after
Kokou no hito-
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Has childhood friends that become jealous of his success in climbing, because their dreams never amounted to anything
Scarlet palace-
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There’s this bit where we find out about the past between the king and the chief eunuch the mc likes and finds out that they were childhood friends and they're in a relationship (maybe, maybe not don't entirely know for sure) and that he's not a eunuch...so childhood friend becoming king and riding on his success kind of story
Kuroko no basuke-
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Has childhood friends who were on the same basketball team in middle school, all on different teams and in different high schools. Then they all compete against each other and so has various members of them victorious at different times
Cat street-
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If my memory is correct, it was the fact that her friends were becoming successful or finding their place in life that pushed her to try to sort her life out
Scarlet chair-
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Childhood friend in poverty becomes king
Savage garden-
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Two orphans in an orphanage, a boy and a girl and the boy finds out that he's got a father that’s a noble. He sends him a letter and then is invited to become the nobleman's successor (or something) but something goes wrong and the girl becomes successful instead
Berserk-
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Childhood friend of the mc becomes really successful in combat and gains favour with the king but then....things go a bit wrong
One piece-
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Has various childhood friends and loved ones that follow the successes and adventures of the crew
Kizu-
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Kind of victorious in his own slightly morbid way lol. MC's childhood friend becomes really good at using his super power...
Good witch of the west-Spoiler (mouse over to view)
MC's childhood friend becomes victorious in his quest for the truth of the world, which the mc strives to help him pursue
Pandora hearts-
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mc goes off into a parallel dimension thing for a time and when out many years have passed and his friend that was once quite weak-willed became a strong adult, but he still has his normal body
Chihayafuru-
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MC discovered the sport/card game because of another boy and when he moves away they promise to keep playing the game and playing in tournaments so they'll meet each other again, but one becomes really good in a short while and stops due to circumstances and the girl mc keeps going becoming higher and higher in the national rankings
Vinland saga-
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well sort of, two of the characters were kind of friends and when ended up being killed, whereas he was at the time a prince that was likely to be killed off, though it depends what you call victoryboth of them achieved things, though the manga asks whats the greater victory