On a day of much action and excitement, it was the nation of Chinese Taipei who stood out the most, with incredible performances from their female team, as all of their young hopes advanced to the quarter-finals.
Bout of the day
The Middleweight class (75 kg) is one of the most competitive divisions in this tournament, and Day 5 saw a clash between two of the strongest boxers in the championships.
Ukraine's defending AIBA Junior World Champion and Agalarov Youth Cup winner Ramil Gadzhyiev faced Ireland's Luke Thomas, a bronze medallist at the 2011 EUBC European Junior Continental Championships in Keszthely, Hungary.
Thomas followed up that accolade with the gold medal in the Irish Youth National Championships, which saw him selected to take part in Sofia.
The Irishman tried to use unexpected tactics against the Ukrainian boxer in the opening round, which caught his opponent off guard.
However, the Odessa-based Gadzhyiev put together some efficient punches from then on, and though Thomas fought hard in the final round, it was the Ukrainian who ultimately proved victorious over his Irish rival in a great match.
Team of the day
The ladies youth boxers from Chinese Taipei can now be thought of as one of the top boxing nations in the world following an amazing team performance on Day 5.
Their Flyweight class (51 kg) boxer Huang Hsiao Wen, a two-time National Champion, started the winning path of Chinese Taipei when she eliminated Poland's EUBC European Women's Junior National Championships silver medallist Wiktoria Sadej.
Huang was the taller boxer, and used her height advantage as a weapon against the European boxer, controlling the bout and winning by unanimous decision.
Huang's compatriot Wu Pei Yi began her boxing career in 2008, and her hard work in the gym is paying off, as seen by her great performance on Day 5.
Though relatively small at 158 centimetres, she made her size work for her, by getting close to her second opponent of the tournament, Australia's Youth National Champion Anne-Marie Kelly.
The Australian was fifteen centimetres taller than her Asian rival, and controlled the opening of the contest, but Wu stood firm, and a slight change of tactics allowed Chinese Taipei's boxer to turn back the fight, eventually winning by split decision.
Chinese Taipei’s AIBA Junior World Champion Chen Nien Chin claimed a bronze medal in the Taipei City Cup last August, ultimately tasting defeat against Kazakhstan's London 2012 bronze medallist Marina Volnova in a close contest which showcased her great potential.
Chen started her boxing career in 2010, and has only been defeated twice in her career. She met with Bulgaria's Youth National Champion Mihaela Nikolova on Day 5, and her strong punches in the first round set the standard for the bout, and she eliminated the home favourite.
This result means that all three of Chinese Taipei's female fighters advanced to the Top 8 in Sofia.
AIBA Road to Sofia boxer of the day
Syria's best youth boxer Ahmad Ghossoun was a silver medallist at the ASBC Asian Youth Continental Championships in Bangkok three months ago, which explains his invite to the AIBA Road to Sofia Program.
Ghossoun has been involved with the Syrian national squad since 2011, and following his opening victory in the championships, he was the favourite against Philippines' inexperienced Sammy Bernabe Junior in their Light Welterweight class (64 kg) bout.
Ghossoun impressed with his footwork throughout, and dominated the final round, which bodes well for the rest of his tournament.
Surprises of the day
Sweden's Araik Aluje Ismail eliminated Greece's Alexandros Farrell in the opening round, which was an expected result for the Northern European boxer.
Ismail was born in Armenia, but after his parents moved to Sweden he started his boxing career in the town of Kristiansand.
In his second bout of the competition he came up against Bulgaria's EUBC European Schoolboys Championships silver medallist Kristiyan Doychev, who was the favourite to progress.
Ismail exceeded expectations however, and shocked the host nation’s experienced youth boxer. His clear victory saw that he advanced to the last sixteen at the Light Welterweight class (64 kg).
Hungary's Youth National Champion and Julius Torma Memorial Tournament winner Richard Toth has won eight out of his ten previous international contests, but one of those two defeats was suffered at the hands of Germany's Pavlyukov Youth Memorial Tournament silver medallist Wladimir Fruehsorger in February.
The 17-year-old Hungarian boxer defeated Kyrgyzstan's best hope Yktiyar Shabdanbayev in the first round, and went on to win his rematch with Fruehsorger via unanimous decision in his second match in Sofia.
Ones to watch
Poland's Elzbieta Wojcik earned a silver medal at the last edition of the AIBA Women's Youth World Championships in Albena, losing in the final to the London 2012 Champion Claressa Shields in a narrow bout.
The Polish Middleweight class (75 kg) boxer is now 18, and has come to Bulgaria for gold, and to qualify to the Nanjing 2014 Youth Olympics.
Wojcik made short work of her fight on Day 5, knocking down her inexperienced Hungarian opponent Nikolett Szabo.
Ukraine's two-time EUBC European Junior Champion Viktor Petrov has had more than two hundreds bouts during his career which began back in 2003.
Petrov has had some unexpected losses over the past year, but looks back to his best form now.
Ukraine's gold medal contender won his second bout in Sofia, proving too slick for Chinese Taipei's Pan Hung Ming, advancing to the third preliminary round.
Australia's AIBA Junior World Champion Satali Tevi Fuimaono opened with an easy triumph in the first preliminary round, but he had a far tougher proposition on Day 5 against the US Youth National Champion Charles Conwell.
The Samoan-descent Austalian boxer had a slow first round, but he was able to step on the gas as the fight progressed, and his extra efforts resulted in a hugely impressive victory.
Fuimaono is the one of the biggest gold medal contenders of the Middleweight class (75 kg), and has looked excellent in Sofia so far.
Stat of the day
In the female part of the championships, the preliminaries are over with the three weight classes edging closer to the medal matches.
Only Chinese Taipei and Turkey have three female boxers left in the competition, while Ireland, Italy, Kazakhstan and United States of America have two athletes remaining in Sofia.
Showing the worldwide strength of female boxing, sixteen nations have still got the chance to get at least a bronze medal in the championships.
Quotes of the day
"I went into the ring with the right tactics knowing I could win the bout against the Japanese boxer, and feeling confident was the key in today's bout. I knew I had the reach on her, so used it to my advantage, and also felt really good in the ring," said Great Britain's EUBC European Junior Champion Crystal Barker, who eliminated Japan's AIBA Junior World Champion Kasumi Saeki on the fifth competition day.
"I felt myself pretty confident, and I was really excited to fight in the Armeec Arena again. My tactic was to work forwards and answer with sidesteps if my Dutch opponent attacked. Sometimes I have got stuck in the fights, but it felt like I handled it good by keeping my arms inside of hers. I will do my very best in the quarter-finals but until that I will relax," added Sweden's AIBA Women's Youth World Champion Agnes Alexiusson following her victory over Netherlands' Bobbi Been.
Three programs are scheduled for the sixth competition day, with only the male boxers in action, spread over four weight classes.
Winners of the Light Flyweight class (49 kg), Lightweight class (60 kg), Welterweight class (69 kg) and Light Heavyweight class (81 kg) bouts will reach the Top 16 on Day 6.
One of the most anticipated fights will be held between Kazakhstan's AIBA Junior World Champion Abylaykhan Zhussupov, and Russia's European Junior Champion Temirlan Batdiyev at the Lightweight class (60 kg).