The left-back, who arrived in Portugal from Real Madrid last summer, will move to Serie A once again on loan, with Sassuolo securing a buy option in the region of €9m - the same figure Torino held but ultimately chose not to activate at the end of his half-season stint in the Piedmontese capital.
Real Madrid retain a 50 per cent sell-on clause on the 21-year-old from his original departure, meaning the Spanish club could bank around €4.5m next year should Sassuolo trigger the option.
Obrador came through Real Madrid's academy, progressing via Castilla before a loan spell at Deportivo La Coruna and his move to Benfica last summer, but has struggled to convince at each stop, including during his half-season with the Portuguese club before Torino took him on loan in January.
Despite a modest start, he grew into an effective performer for Torino in the second half of last season, with his eye-catching goal against Cagliari among the highlights of his loan spell, and he remains a left-footed option in a position that continues to attract interest from Serie A clubs.
In total he has made 115 senior appearances across his career to date, including 34 for Real Madrid Castilla and 33 during his loan at Deportivo.
Sassuolo have been searching for reinforcements at both full-back positions this summer, with Parma's Emanuele Valeri also considered as an alternative option on the left, while free agent Matteo Darmian has been mentioned as a possible experienced addition on the right following his departure from Inter.
Obrador's exit also has knock-on implications at Torino, who had viewed him as a potential like-for-like replacement on the left flank had Cacciamani been sold this summer - a route now closed off following his move to Sassuolo.