In 2015 he won the ACBS Asian Under-21 Snooker Championship, beating Yuan Sijun 6–4 in the final and as a result was given a two-year card on the professional World Snooker Tour for the 2015/2016 and 2016/2017 seasons. His first appearance in a ranking event qualifier came at the 2016 World Championship, where he was edged out 10–9 by compatriot Thepchaiya Un-Nooh in the opening round.
Akani qualified for the 2016 Indian Open by defeating Ben Woollaston 4–3 and then saw off Jamie Burnett 4–1, Mark Davis 4–2 and Gary Wilson 4–2 (opened the match with a 104 break) to reach the quarter-finals of the first ranking he had appeared at. He took a 2–1 lead over Kyren Wilson, but would go on to lose 4–2. He also lost in the quarter-finals of the non-ranking Six-red World Championship 7–4 to Stuart Bingham. At the Northern Ireland Open, Akani eliminated Cao Yupeng 4–1 and Mark Davis 4–3 and was knocked out in the third round 4–2 by Wilson. He qualified for the German Masters by seeing off Graeme Dott and Jack Lisowski, but was thrashed 5–0 by Zhao Xintong in the first round. He stood one win away from playing in the World Championship after defeating Mei Xiwen 10–5 and Joe Perry 10–9, but was heavily beaten 10–3 by David Grace. Akani failed to break into the top 64 in the rankings during his two years on tour, but will stay on it by topping the one-year list.
In 2017, he started the season like the year before. He reached the Last 16 of the 2017 Indian Open after beating Scott Donaldson, Stephen Maguire, and Dominic Dale before losing 4–2 to Liam Highfield. At the 2017 World Open qualifying round, he had a close match against Liang Wenbo losing 5–4 after being 2–0 and 4–2 up and scoring back-to-back century breaks (101 and 119) but losing the "decider". At the 2017 International Championship, he was 2–0, 3–1 and 4–2 behind but he won the last 4 frames to beat Marco Fu by 6–4. In the last frame, he cleared the table with a break of 53 to win the frame by 2 points. After a walkover in the last 64, he lost against Martin O'Donnell 5–6, despite a lead of 5–2.
During the 2017 UK Championship, Akani defeated three higher seeds, defeating Fergal O'Brien 6–5, Michael Holt 6–4, and whitewashing former world championship runner-up Barry Hawkins 6–0. After the match, Hawkins said the match "was up there with one of the worst I have ever played". In the last 16, Akani drew Ronnie O'Sullivan and went ahead at scores of 2–0, 4–2 and 5–4, before losing the match 6–5. After the match O'Sullivan stated he believed Akani "deserved to win" and "felt like (he) robbed him of victory".
Akani is known for his very deliberate cue action, where he plants his hand down with the cue before playing the next shot. In the book 147 Snooker Drills and Exercises by Andrew Highfield, he named a challenge after Akani, after challenging him to complete the drill. He is also known for resting his chin on the cue extension when playing with a rest.
- Sunny Akani at worldsnooker.com