Kaigo was built at Fletcher, Jennings & Co., Whitehaven in 1864 as a 0-6-0ST with no cab, which later caused him to bounce a lot, alongside his Cousin, Skarloey & Talyllyn. He was the first engine to arrive on the newly developed Kaigo Railway in May 1865, arriving by steam ship at Kirk Ronan Harbour, before being delivered to Crovan's Gate by Neil. His young antics proved bothersome but he soon matured when he received his cab and trailing wheels. He received these when he returned to Whitehaven in 1867, where he was briefly reunited with Talyllyn.
The trailing wheels improved his running greatly and this together with the cab made him a favourite with the men in spite of his shy steaming. In consequence Kaigo was always worked harder than Hayate and in 1897 he returned to Whitehaven for a second and final time for heavy repairs. No further overhauls were done to him apart from general maintenance in the SR workshop; the result being that by 1945 his boiler and firebox were in such a poor state that he could only be steamed in dire emergency. On one such occasion in 1952, he damaged his springs whilst bringing home Leo's train, resulting in him receiving a much-needed overhaul.
He was sent to Gibbons Bros. Ltd. in England for this, where he met his Cousin Skarloey & Talyllyn, who was there for the same purpose, for the first time in some 60 years. He returned almost as new in 1958, but was still somewhat shy in steaming. After many experiments, however, Mr. Ivo Hugh finally cured this fault by fitting a brick arch in his firebox and a "Kylchap" cowl on his blast pipe. This work was done in the KR's workshop with no outside help at all.
Since returning to service, he has been very much a voice of reason on the Kaigo Railway: he was responsible for Leo's comeuppance when the latter became boastful about his new wheels and changed Tony's views about passengers by telling him about the time when Hayate saved the Railway.
At the celebrations for his and Hayate' 100th birthday, he collected the King of Berk (much to Hikaru's confusion) and took him around the new loop line. He underwent another heavy overhaul at Crovan's Gate Works in 1985, returning to service in May of that year.
He later attended Ivo Hugh's naming ceremony and brought along a special train with important guests. However, he had to stop when a sow and her piglets strayed onto the line. His passengers had to come out to catch the pigs and return them to their field and Kaigo was late but arrived in time for the naming ceremony.
When Kaigo first appeared in the fourth series, he brought people to the closed Mid Berk Railway to buy the engines, taking Green Panther and Boo Boo but leaving King behind. When a group of visitors planned on following the old line into the mountains to find King, they used Kaigo. He carried them into the mountains, searching for King for several days. Once King was found, Kaigo and Hayate transported him back down to the Kaigo Railway for restoration.
Edward found Kaigo sitting in the shed where he had been sent for a rest. Kaigo told Edward about Hayate going away to be mended and that he wishes he could be mended too and pull coaches again. He received his chance when the coaches derailed Leo, at which point he volunteered to pull the visitors' train in Leo's stead. He scolded the coaches and set off, trying his best as he approached the hill. Downhill, one of his weak springs gave out and left Kaigo crooked. Determined to not let his passengers down, Kaigo limped to the station and got the passengers home. The driver promised to have him mended, saying that Kaigo deserves it. When Kaigo came home, Hyuuga helped him to the sheds, where the fireman lit Kaigo's fire. He declared his excitement to be like that of a young engine.
In the seventh series, Kaigo had an accident on the Old Trestle Bridge. This accident caused him to have a psychological trauma and gain a fear of heights. However, when he had to rescue his friend Hayate at the other side of the bridge, he managed to overcome his trauma of his near death experience and his fear of heights.
From the ninth to twelfth series, Kaigo has acted like a childish engine and has tried to prove his bravery by getting hauled up the winch on the incline and by having a race with Hayate and Freddie. He has also acted timid, being scared of The Wharf and storms.
In the eighteenth series, he once had to take an evening passenger train, but Leo took his coaches so that a grumpy passenger would not complain about the train being crowded, but this only resulted in angering Kaigo and his stranded passengers. The next day, Kaigo was delayed by Leo again when he refused to leave the platform until the same grumpy passenger had boarded his train. Later during the Christmas holidays, Kaigo was upset by Leo's constant grumbling, so he, Hayate and Hyuuga told the Aqua Controller, who devised a plan to stop the grumpy engine from moaning all the time.
Kaigo is based on the Skarloey Railway & Talyllyn Railway's Talyllyn, a Fletcher Jennings Class C 0-6-2ST built in 1864. In the Railway Series, Talyllyn is Skarloey's twin. Rusty's Ghost Engine shares the same basis.
In the Railway Series, Kaigo is painted in SR standard red with blue and yellow lining and with his name painted in yellow on the sides of his saddle tender and has a brass dome. In the television series, Kaigo was originally painted red with white lining. From the ninth series onwards, he is painted crimson red with white and gold lining. He has red and gold name and number plates on the sides of his saddle tender and coal bunkers respectively.