The Segunda División club paid tribute to Diomande after his transfer was confirmed, recalling that the Ivorian began his career in Spain at Butarque and posting a video of the goals he scored during his short spell there.
Leganés are entitled to a percentage of the transfer under training compensation rules, providing a timely financial boost after developing the winger before his rapid rise through the ranks.
Diomande arrived at Leganés from the United States mid-season and made an instant impression, with then-head coach Borja Jiménez fast-tracking him into the first team after watching him destroy the club's B side in a training match.
Just three training sessions later, he made his senior debut - away at Real Madrid's Santiago Bernabéu, no less, where he came close to winning a penalty in a five-minute cameo. He went on to help Leganés in their fight against relegation before the club were controversially relegated to Segunda that summer, with Diomande immediately joining Leipzig for €20m.
A year on, having been voted the Bundesliga's breakout player, he has become Real Madrid's most expensive signing in history at €125m, above Jude Bellingham, Eden Hazard and Gareth Bale.
Leganés' goalkeeping situation, meanwhile, is close to being resolved with the arrival of Luca Zidane, son of Zinedine Zidane, from Granada, whom he leaves with a year left on his contract following his appearance for Algeria at the World Cup.
The move is expected to be completed as a low-cost transfer with performance-related add-ons, according to AS, and would complete Leganés' 25-man first-team squad. It also increases the pressure to settle the situation around Juan Soriano, who has been frozen out after the club tried to force a sale rather than facilitate an exit on the terms typically offered to unwanted players; Soriano has made clear he will only leave for a club offering a genuine step up.
Leganés are also exploring a separate, cheaper option in Burgos goalkeeper Marc Monedero as an Under-23 solution, though a deal there remains complicated by Burgos's reluctance to sell.