Here is some information which may help (credit Mark Kaiser, 1997-98, "Unit structure of IJA Air Force"):
The Sentai
A typical Sentai was a single-purpose unit consisting of three Chutai divided into three Shotai (flight) of three a/c each. Together with the machines of the Sentai Hombu (HQ flight) and the reserve a/c, nominally amounting to some 1/3 of the Sentai strength, the total number of aircraft in a regular fighter Sentai amounted to 45.
A few figter Sentai consisted of four Chutai, while most bomber or reconnaissance Sentai numbered only two and totalled up to some 30 aircraft.
In April of 1944 the structure of a Sentai was redesigned. Thus far, a Sentai was a pure air unit, while the maintenance and other ground services were conducted by other, separate units. From now on, they were all incorporated into the Sentai which, in turn, was divided into an air section called Hikotai (air unit) and a ground section called Seibutai (maintenance unit).
The Hikotai itself was divided into Kogekitai (assault units). It was no more than a new, fancy, morale-boosting name of the old Chutai. It didn't stick among the ranks and the Chutai - label remained in use throughout the war. The only practical consequence of this last structural change was the fact that the Sentaicho (the Sentai commander) was now in charge of a larger unit, while the new functions of a Hikotaicho and a Seibitaicho were instated for the command of the air and ground sections.
Flight, maintenance and communication schools acted as separate units with their own specific insignia and names, under the direct command of the Koku Hombu (JAAF HQ). Separate training or second-line units, and also later in the war combat units, were sometimes created within the schools. They were gradually incorporated into the regular structure on a proper level of command, keeping the original names.
Unit..............American equiv.........Makeup........................# of planes..........CO
Shotai...........flight...............................n/a.....................................3 planes...................n/a
Chutai...........squadron.......................3 Shotai...........................9-12 planes...........Captain
Sentai...........group..............................3-4 Chutai.......................36-45 planes..........Lt col/Maj
Hikodan........wing...............................2-3 Sentai + 1 Chutai..110-150 planes.....Colonel
Hikoshidan..air division..................2-3 Hikodan....................300-450 planes.....General
Kokugun.......air force........................2 Hikoshidan..................600-900 planes.....General