~こと請け合い => I guarantee ... N1
Happens next
合う => do something together N3
[合「あ」]う => To do A together/mutually N4
Secondary Verb
場合(は) => in the event of; in the case that ~ N4
~ににあわず (に似合わず ) => ~Different from N1
Evaluate
もともと => originally,by nature,from the start N3
Invariant
~と(も)なると/と(も)なれば => ~Just, whenever, once N1
Condition (hypothetical condition)
~ものとおもう => Believe~ N1
Speculation
ともすると => Perhaps, maybe N3
Base, base
…てもともとだ => originally, by nature, from the start N2
Change the subject of the story
もし~としても/もし~としたって => Assuming; Even if ~ N3
もっとも => but then; although; though ~ N2