eight

Eight is an orange robot deeply in love with his creator. Designed by the Sanzenin Technology Division to be the ultimate nursing robot, he boasts features such as waterproofing, "nursing missiles," and rocket boosters. However, Eight's quick temper often leads to his downfall; he becomes enraged when called "ugly" and seeks revenge after being defeated. His dialogues reveal that his actions are driven by a desire to prove himself to his beloved creator. Unfortunately, Shiori tends to dismiss him, even going so far as to label him a "mistake" and suggesting he should be incinerated instead of properly disposed of. Despite this, Eight gets a second chance after his latest upgrade, eventually becoming Shiori's boyfriend after confessing his feelings. Prior to each appearance, Eight receives an upgrade: v8.1 after his first defeat, v8.2 before meeting Hayate at the amusement park, v8.3 upon forming a couple with Shiori, and further upgrades following Shiori's transfer to Hakou Academy. In the anime, Eight self-upgrades to v8.1 after stealing Nursing Robot Nine's control chip and reaches v8.2 in his second form, but reverts back to v8.1 after being defeated by Yukiji and Hayate.
(Source: Hayate no Gotoku! Wiki)